television made easy' building a 15c.c.model two … · 2019-10-23 · 140 persons, will be...

TELEVISION MADE EASY' BUILDING A 15c.c.MODEL TWO-STROKE PETROL ENGINECHEMICAL EXPERIMENTS WITH SELENIUM 'BUILDING A FINE MODEL SPEEDBOAT*A HOME-MADE RELAY MODEL ELECTRIC RAILWAYS THE MONARCH TWO-VALVERnECTRIC LIGHTING FOR MODELS FACTS ABOUT AIRCRAFT' SCALE MODEL NIGH -SPEEDFURY * PLASTIC MOULDINGS* LATEST TOOLS CLEVER IDEAS* PATENT AD ETC,

www.americanradiohistory.com

86, St. Peter's Grove,Canterbury.

Class Number 17th Dec., 1934.L 131682.Dear Sir,

You may remember me as a pupilof your College, taking a correspondencecourse for the recent Civil ServiceExamination. The result of this examina-tion has now been published and I learnthat I was fortunate enough to secure thetop place out of over 1 ,400 other candidates.I consider that this result reflects greatcredit upon your course and your tutors,for their interest and their willingness tohelp me with my studies.

May I wish you the compliments ofthe season and every success in the future.

Yours very gratefully,C. P. Cayley.

3LETTERSRead them then youwill realise what is

happening and why.

A VOCATIONAL TRAINING

FROM THIS COLLEGE IS A

CAREER-A SUCCESSFUL

PROGRESSIVE CAREER

110, Victoria Road, Dundee,Angus.

16th January, 1935.

MR. J. H. BENNETT,Bennett College Ltd.,

Sheffield.

Class Number L159929.

Dear Sir,A short time ago I enrolled as astudent of the Clerk of Works

Architecture, etc., course ; although stillin my twenties, I have, through theexcellent tuition provided in the abovecourse, been successful in my applicationfor the position as Clerk of Works withthe Dundee Town Council.

Yours faithfully,George Moffat.

OPEN LETTER TO PARENTSDear Sir or Madam,-When your children first arrived they brought with them a wonderful lot of sunshine. Later you becameproud of the intelligence they displayed, but still later you became anxious as to what would become of them in the future. Perhapsyou were anxious when you visualised them as grown men and women. Even with plenty of money it is not always easy to selectthe right career, and a parent is sometimes inclined to ask advice of some relative and in ninety-nine cases out of a hundredthat relative knows nothing at all about the possibilities of employment. Why not let me relieve you of some of your anxieties?In fact, why not let me be their Father ? We do not profess to act as an employment agency, but the nature of our business com-pels us to keep an eye upon the class of men and women that are wanted and who wants them. There are some people whomanufacture an article and put it on the market to sell. We do not do that, we work in exactly the opposite direction. We find outwhat employers want and we train our students to fill those jobs. We have to be experts in thematter of employment, progress and prosperity. If you have any anxieties at all as to what yoursons and daughters should be, write to me, or better still, let them write to me personallyFatherly Advice Department --and tell me their likes and dislikes, and I will give sound, practicaladvice as to the possibilities of a vocation and how to succeed in it. Yours sincerely,

CAN YOUCHANGE MYEXPRESSION

IF SO, YOU MAY BETHE ARTIST THATCOMMERCE IS

WAITING FOR

Just try it for yourself,trace or draw the out-cpy, line andte

feature.t he put in

4.4 Cfl

There are hundreds of openings in connection withHumorous Papers, Advertisement Drawing, Posters,Calendars, Catalogues, Textile Designs, Book

Illustrations, etc.6o per cent. of Commercial Art Work is done by" Free Lance Artists " who do their work at homeand sell it to the highest bidders. Many Commer-cial Artists draw " retaining fees " from varioussources, others prefer to work full-time employmentor partnership arrangement. We teach you notonly how to draw what is wanted but how to makebuyers want what you draw. Many of our studentswho originally took up Commercial Art as a hobbyhave since turned it into a full-time paying profes-sion with studio and staff of assistant artists ; thereis no limit to the possibilities. Let us send full par-ticulars for a FREE TRIAL and details of our coursefor your inspection. You will be under no obliga-tion whatever.

c94---41-441IT IS THE PERSONAL

Art Dept. 76.

YOU CAN HAVE A COLLEGETRAINING IN ALMOST ANY CAREERFOR A FEW SHILLINGS MONTHLYAccountancy ExaminationsAdvertising and Sales

ManagementA.M.I. Fire E. Exam.Applied MechanicsArmy CertificatesAuctioneers & Estate AgentsAviation EngineeringBankingBoilersBook-keeping, Accountancy

and Modern BusinessMethods

B.Sc. (Eng.)B.Sc. (Estate Management)Building, Architecture and

Clerk of WorksCambridge Senior School

CertificateCivil EngineeringCivil ServiceAll Commercial SubjectsCommercial ArtConcrete and Structural

EngineeringDraughtsmanship. All

branchesEngineering. AU branches,

subjects and examinationsGeneral EducationG.P.O. Engineering Dept.Heating and VentilatingIndustrial ChemistryInsurance

MathematicsMatriculationMetallurgyMining, all subjectsMining, Electrical

EngineeringMotor EngineeringMotor TradeMunicipal & County EngineersNaval ArchitecturePattern MakingPolice, Special CoursePreceptors, College ofPumps and Pumping

MachineryRadio Service EngineeringRoad -Making and

MaintenanceSalesmanshipSanitationSecretarial Exams.ShipbuildingShorthand ,Pitman's)Structural EngineeringSurveyingTeachers of HandicraftsTelephony & TelegraphyTransport Inst. Exams.Weights and Measures

InspectorWeldingWireless Telegraphy and

TelephonyWorks Managers

If you do not see your own requirements above,write to us on any subject.

TOUCH WHICH COUNTS IN

HOW TO STUDYIn your spare time when it suits YOU.You fix your own time, you do not GOto your studies-the postman bringsTHEM TO YOU. There is nothing thata class -room teacher can show on a black-board that we cannot show on a whitepaper. The lesson on a blackboard willbe cleaned off, but our lessons arePERMANENT. A class -room teachercannot give you a private word ofencouragement, but a CorrespondenceTutor can do so whenever your workdeserves it. On the other hand he can,where necessary, point out your mistakesPRIVATELY.

TO STUDENTSLIVING ABROAD

or on the high seas, a good supply of lessonsis given, so that they may be done in theirorder, and despatched to us for examination andcorrection. They are then sent back with morework, and in this way a C0,111:1114014S stream of workis always in transit from the Student to us andfrom us to the Student, therefore distance makesno difference.

Also ask for our New Book(Free of Charge)

THE HUMANMACHINE

SECRETS OF SUCCESS

POSTAL TUITION

YOUNG MENYoung men physic-ally fit and whosecareers are not defin-itely fixed should jointhe Police Force. Wehave Special Coursesfor Entrance andPromotion.1 I per week brings

success. Fullparticulars free.Address : Police Dept. 78

FOUNDED 1900.

Dept. 76, THE BENNETT COLLEGE, SHEFFIELD.

EVERYDEPARTMENT ISA COMPLETECOLLEGE.

EVERYSTUDENT ISA CLASS TO

HIMSELF.

All applications respecting Advertising in this Publication should be addressed to the ADVERTISEMENT MANAGER, GEORGE NEWNES Ltd.,8.11 Southampton Street, Strand, London, W.C.2. Telephone: Temple Bar 7780.


April, 1935 NEWNES PRACTICAL MECHANICS 297

racticd1Mechan_ics

SUBSCRIPTION RATES : Editorial and Advertisement Office : "PracticalMechanics," George Newnes Ltd., Southampton

Inland and Abroad, 7s. 6d. per annum Street, Strand, W.C.2.Registered at the G.P.O. for transmission by

Canada - 7s. per annum Canadian Magazine Post

VOL. II. No. 19

APRIL1935

Notes, News and ViewsOxy-Ferrolene

ACHEAP substitute for acetylene for usein oxy-acetylene steel -cutting blowpipes

was demonstrated in London recently. Thesecret of this is a liquid called " Ferrolene,"which is said to be a volatile petroleumproduct. Compressed coal -gas is bubbledthrough this liquid. The mixture of coal -gas and Ferrolene vapour is then fed to aspecial oxy-blowpipe. Oxy-Ferrolene willdo the same amount of cutting as oxy-acetylene at about half the cost. It is saidto give a cleaner cut. The Oxy-Ferroleneflame also gives no incandescent glare. Thediscovery should make the use of the blow-pipe in cutting thick steel even morepopular than it already is. A Sheffield firmrecently used the process for cutting througha propeller shaft 36 in. in diameter.Temperature Changes

TINY changes in temperature caused bycompression and expansion in the air

as sound -waves pass through it are beingmeasured by Ellis A. Johnson of the Massa-chusetts Institute of Technology. Theinstrument used can measure the " heat "of sounds too feeble for the ear to detect.Testing Aviators for Altitude Flights

AT Monyecelio aerodrome in Rome aspecial room has been built where

aviators can be examined by doctors beforeand after altitude flights to discover thestate of their physical reactions to condi-tions. In this room, which is of 30 cubicmetres, a special pump run by an engine of16 h.p. creates a depression which can beequal to 16,000 metres of height. A coolingapparatus cools the temperature which canbe lowered to about 70° below zero. Theroom is fitted with instruments of all kinds,and blood tests are made as well as tests ofthe organs.A New French Rail CoachAN oil -driven streamlined rail coach,"which arrived in England from France,recently made a full -speed trial run on theL. M. S. railway between Willesden (London)and Tring (Hertfordshire). The new coach isequipped with rubber tyres and carries twospare wheels. It can be driven both back-wards and forwards, and is said to be cap-able of a speed of ninety-five miles per hour.

The Largest Fish Port in the WorldAT Grimsby a short time ago Sir Henry

Betterton opened a £1,700,000 fish dock,the largest of its kind in the world. It hasa total water area of 35 acres, and bringsthe total water area of the port up to64 acres, making it the best equipped in theBritish Isles for landing fish. Twenty-three new trawlers are already under con-struction as a result of the new dock. Lastyear Grimsby marketed 186,000 tons of fish-one -quarter of the whole catch landed inEngland and Wales.

THE MONTH'S SCIENCESIFTINGS

The new Cunarder" Queen Mary " is tobe equipped with twenty-eight all -steel life-boats, each weighing 16 tons fully loaded.The boats, which will each accommodate140 persons, will be propelled by high-speed Diesel engines.

A strange -looking aircraft, a taillesstwo-seater fighting 'plane, built for theRoyal Air Force, was recently demon-strated at Yeovil. Pilot and observer havean uninterrupted view all round.

A new British colour -film process wasrecently demonstrated in London. Thefilm shown was a travel -picture of Devon-shire, in which reds and blues wererendered with considerable fidelity. Thecolour is produced entirely through thelens, and the problem of focus is elimi-nated.

The Loudest SoundTHE loudest sound ever heard by man was

the eruption of Krakatoa, a volcano inthe Dutch East Indies, in 1883. So violentwas the explosion that air waves resultingfrom it travelled three times successivelyround the world.

A New Transparent Synthetic ResinA NEW synthetic resin known as"" Leukon " has recently been producedwhich is insoluble in water, alcohol, andaqueous media, and is unaffected by acids oralkalis up to concentrations of 40 per cent.

in the case of sulphuric acid and of causticsoda at atmospheric temperatures. It isalso unaffected by many high boilingorganic esters. It is soluble in certain ofits forms in a number of organic solvents,which include acetone, chlorinated hydro-carbons and benzene.

Leukon's low thermal conductivity andattractiveness to touch, especially whentaken in conjunction with its mechanicaland chemical excellence, suggest manypossible uses in the field of medical andhospital equipment. It should be remem-bered that Leukon is more resistant tomoisture and can have a higher softeningpoint than ebonite, while it has the stillfurther advantage of a wide range in colouras well as transparency. Closely linkedwith the medical field is the possible manu-facture of Leukon spectacle frames by theinjection moulding technique. This wouldgive a frame which is kind to the wearer,tough, strong, light in weight, unlikely tosplit, warp, or be affected by moisture orperspiration.

World's Steam Locomotive RecordTHE London and North-Eastern Rail-

way locomotive, Papyrus, which set upa world's speed record for steam locomo-tives of 108 m.p.h., was lubricated withoil produced by the makers of WakefieldCastrol.

Making Glass WoolSHREDDING glass into woolly fibres

by centrifugal force is the uniqueprocess developed by a Swedish manu-facturer of glass wool. Melted glass runsdown upon a disc, which rotates withgreat velocity. By action of the centrifugalforce, the glass is disintegrated into a massof extremely fine threads. A current ofair is blown downward around the edge ofthe rotating disc, carrying the formedglass wool down upon a cutting andtransporting apparatus, by means of whichthe product is continuously carried awayfor further working. The fineness of theglass threads can be controlled withincertain limits by regulating the temperatureof the melted glass and the amount ofglass fed upon the rotating disc per unitof time.


298 NEWNES PRACTICAL MECHANICS April, 1935

A ariei,anrertTHE same love of adventure

which through the ages hasprompted man to explore

the whole habitable surface ofthe earth exerts its influence still,and he is nowadays tempted toenter realms whose barriers, notmany years ago, were to himutterly impregnable. He hasrecently conquered the air toan extent previously undreamtof, but no voyage to the strato-sphere can compare in interestto exploration in the depths ofthe sea, with its myriad livingthings, beautiful or grotesque,timid or formidable, cataloguedor unknown.

Unlike aviation, deep-seadiving has been carried on in aprimitive way for centuries. SirRobert H. Davis,in a recent seriesof lectures before the RoyalSociety of Arts, cited Pliny's" Historia Naturalis " (A.D. 77),in which are mentioned divers,employed in warfare, who drew airin through tubes, one end of whichthey held in their mouths, while theother was supported at the surfaceby a float. This practice is com-

'1 I

IIII 1

I '1'

Mysteries beneath the sea have been examinedchiefly in the interests ofscience. This article explainssome of the methods of overcoming the difficulties

of penetrating into the depths of the ocean.

Sightseers descending to the floor of the Pacific, 100 ft. below the surface,four miles off shore, and come up without even damping their shoes.

pared to that of an elephantwhich can breath through itsuplifted trunk while its bodyremains submerged. The lectureremphasised the fact that it wouldbe possible only to use thissystem in a very few feet ofwater, since, on breathing theair through an open pipe, thelungs would be exposed toatmospheric pressure only, whilethe body would be subjected toincreased pressure varying withthe depth of the submerged diver.This would produce a dangerouscompressive effect on the lungs,and result not only in greatmuscular effort in inhaling, butalso in the production ofhemorrhages in the diver'sair -way.

Modern Diving DressApparently Sir Robert, who is

governing director of Messrs.Siebe Gorman & Co., Ltd., sub-

marine engineers, regards the" open " diving dress of AugustusSiebe, introduced in 1819, as thefoundation upon which moderndivine dress has hrq-n ciPvelorpri.

Captain C. B. Mayo broke all existing U.S. Navy diving records at Seattle when hedescended 400 ft. into the waters of Puget Sound in a demonstration of the Romanodiving bell which marine experts believe will revolutionise existing salvage methods.The bell is the invention of Gene Romano, a mechanical engineer. The inventorclaims the bell to be especially adapted to raising sunken submarines and deep sea mine -laying, as well as to commercial diving purposes. It is seen poised at the end of thederrick which lowers and raises ii from the water. It is a heavy metal pear-shapedglobe capable of withstanding enormous under -water pressure. In the conning -tower -like top are glass port -holes, under which the occupants of the globe, two innumber, may observe their manipulations of the articulated arms extending out fromit. The dexterity of these is such that a small coin may be picked up with the finger -like claws at the end. Lines and couplings may be handled by them with ease as wellas acetelyne blow torches. The bell carries a sufficient supply of air, supplementedwith oxygen tubes, to maintain two men (rider water for fifty-four minutes. The bellis connected with the surface crew by two telephone lines, and a battery of four high -power lights attached to the mobile arms provides brilliant under -water illumination.



In this the wearer had to be cir-cumspect in his movements, since, if hebent down, he ran considerable risk offilling his helmet with water. Still, muchgood work was done with it, and it was notlong before Siebe introduced his closeddress and helmet. In this it was madepossible for the diver to be supplied withcompressed air, the appropriate density ofwhich he could regulate himself by meansof an adjustable spring valve, similar inoperation to the well-known safety valves ofsteam engines. Towards the conclusion ofthis article further reference will be madeto Sir Robert H. Davis, whose extensiveknowledge of the subject enabled him todesign the submarine escape apparatuswhich bears his name.

Salvage OperationsModern diving dress mainly owes its

being to the desirability of carrying outsalvage operations on sunken shipping. Anillustration accompanying this article showsdiagrammatically the system employed bythe salvage ship Salvor in its efforts toreclaim from the sea the fortune in gold,silver. and precious stones which sank withS.S. Merida when she was rammed by theAdmiral Farragut. In this case the depth itwas necessary to descend was 200 ft.Captain C. B. Mayo broke all existing U.S.Navy diving records at Seattle when hedescended 400 ft. in a demonstration of the" Romano diving bell," also illustrated,which marine experts believe will revolu-tionise existing salvage methods. The bellis the invention of the mechanical engineer,whose name it bears. The inventor claimsthe bell to be especially well -adapted toraising sunken submarines and to deep-seamine -laying, as well as to commercial divingpurposes. It is shown poised at the endof the derrick, which lowers it and raises itagain from the water. It is a heavy metalpear-shaped globe, capable of withstandingenormous under -water pressure. In theconning -tower -like top are glass port -holes,from behind which the two occupants mayobserve their manipulations of the articu-lated arms extending out from it. Thedexterity of these is such that a small coin

may be picked upwith the finger -likeclaws at the end.Lines and couplingsmay be handled bythem with ease aswell as acetyleneblow -torches. Thebell carries asufficient supply ofair, supplementedwith oxygen con-tainers, to enablethe two occupantsto remain under-water for approxi-mately an hour.The bell is con-nected with thesurface crew by twotelephone lines, anda battery of fourhigh -power lightsattached to themobile arms,provides brilliantunderwaterillumination.

The Record DepthAnother interest-

ing form of divingdevice was that inwhich Dr. WilliamBeebe, the marinebiologist, who hasbeen described asthe " ProfessorPiccard of theOcean," recentlymade a descentof 2,500 ft.-morethan half a mile-beneath the sur-face-the greatestdepth everattained by manunder water. Onlythe fact thathis oxygen supplywas running short prevented Dr. Beebefrom going lower into the unknown depths

Diving apparatus of varioussunken freights which arevessel here shown, the S.S.

The huge specimen of coral shown here was gathered under the direction of f. E. Williamson. who.. under -seaphotography is famous. It measures 16 ft. by 14 ft.. and weighs 4 tons.

kinds owes its inception to the desirability of salvagingvalueless unless they can be reclaimed. The wrecked

Merida,- was laden with gold, silver and preciousstones.

of the sea. As it was, Dr. Beebe madeobservations which enabled him to namefive or six hitherto unknown fish, andcollected scientific data of great importance.He was accompanied by Mr. Otis Barton,the inventor of the " Bathysphere," as theapparatus was named. This record descentunder water was made at Bermuda.

Often the devices which enable a numberof persons to descend below the surface ofthe sea are erroneously called " diving bells."Strictly speaking, a diving bell is open atthe bottom, the pressure of air within pre-venting the water from entering. If aninverted cup or glass tumbler is immersedand held under water, the imprisoned airwithin seeks to escape vertically upwardsbut is unable to do so. As soon, however,as the cup or tumbler is tilted to anymarked extent from the vertical, the airwill begin to escape from beneath, and willrise in large bubbles to the surface. Thisprinciple has been used to enable work tobe carried out on shallow ocean beds bymen above whose heads is suspended anair -tight dome -shaped structure containinga continually replenished amount of air.Hence the name " diving bell," since itresembles in essential shape the familiarchurch bell.

For SightseersOne of the accompanying illustrations

shows a " diving bell," (though not, forreasons just explained, strictly such) fordeep-sea sightseers, in which they maydescend 100 ft. or more below the surface,and come up, as it is explained to them,



" without even damping their shoes." Thusare they able to peer into some of themysteries of deep-sea life. The under-water chamber is lowered by a crane fromthe deck of a steamer. It is weighted with

The closed diving dress introduced by Augustus Siebein 1837. In this the diver was enabled for the firsttime to control the pressure of the air he breathed to

suit the circumstances of his immersion.

1,500 lb. of ballast necessary to overcomeits buoyancy, and reaches the limit of itsrun in about a minute. Each of the passen-gers aboard is able to look outwards intothe water through thick -glass observationwindows. An electrically -driven air -purifier is in operation all the Urn& and incase one of the windows should break underpressure, steel flaps can be tripped intoplace, hermetically sealing the breachbefore an appreciable amount of water canenter. There is sufficient oxygen within the" bell " to last the occupants from six toeight hours.

" One-man Submarine "A deep-sea explorer, aided by his experi-

ence in the construction of submarines.recently built a diving apparatus that holdsone man in an adjustable case. Thisapparatus replaces a vessel requiring a crewof several men. The suit rather resembles aknight's armour and the turret -like bodyis like the conning tower of a submarine.This " one-man submarine," as it has beendescribed, can dive to a depth of more than800 ft. in ten minutes, the ascent fromthis depth only requiring about fourminutes.

Many readers will remember having seenexcellent cinematograph pictures takenunder the sea. The originator of under-seas photography was J. E. Williamson,who during six months spent under thewaters surrounding the Bahama Islands inquest of specimens for the Chicago FieldMuseum, took many films, through glassmany inches thick, of the mysterious floorof tropical seas. His " studio " wasapproached along a long flexible metal tubewith a boat as its base. Probably the largestcoral specimen ever taken from the bed ofthe sea was gathered by him, and is illu-strated here. It measures 16 ft. by 14 ft.,and weighs 4 tons.

Escaping from sunken submarines hasalways presented a considerable problemfor many reasons, most of them bound upwith an elementary principle of hydro-statics, whereby pressure increases accord-ing to depth reached. The pressure of airwithin a submarine must approximate tothe pressure without, before hatches can beopened, and also some form of air lock mustbe incorporated in order that the openingof a hatch may be unaccompanied by anyconsiderable entry of water. The Davisescape apparatus marks a considerable

advance in permitting the members ofcrews of disabled submarines to reach thesurface in safe -compact,means wherebya sufficiency oftime of releaseopened hatchthe surface

ty, supplying inportable form aa man may haveoxygen from thefrom theuntil he reachesabove.

Replacing a vessel requiring a crew of several men,this " one-man submarine; as it has been called,enables research work to be carried out on the bed of

the sea that would otherwise be impossible.

ROYAL AIR FORCEIT is announced by the Air Ministry that

about 500 vacancies will occur in August,1935, for well-educated boys to be trained

as aircraft apprentices in the followingskilled trades of the Royal Air Force :fitter, wireless operator, mechanic andinstrument maker. Full particulars re-garding entry and conditions of servicemay be obtained from the Secretary, AirMinistry (Apprentices Dept.), GwydyrHouse, Whitehall, London, S.W.1. Appli-cants must have attained the age offifteen years and be under the age of seven-teen years on August 1st, 1935. A com-petitive examination will be conducted atnumerous local centres early in June, 1935,the subjects being English and GeneralKnowledge, Mathematics and Science.Applicants possessing an approved firstschool certificate with specified credits maybe excused the entrance examination. Noprevious trade experienoe is required. The

700 Aircraft Apprentices

and

Boy Entrants wanted

closing date for the receipt of nomina-tions for the August entry, is Tuesday,May 7th.

Further VacanciesAbout 200 boy entrants will also be

required in September and candidatessitting at the aircraft apprentice examina-

tion for whom apprenticeships are notavailable, may, if of suitable age andeducational attainment, be offered enlist-ment as boy entrants to be trained in thetrades of armourer, photographer andwireless operator.

Excellent OpportunitiesThe Royal Air Force offers excellent

opportunities to well-educated boys ofsecuring an efficient training and of embark-ing on an interesting career with manypossibilities of advancement. Aircraftapprentices and boy entrants are housed,fed and clothed free of cost and receivepay. The training is in the hands of well -qualified technical instructors, and boysentering as apprentices continue theirgeneral education throughout the appren-ticeship period under a staff of graduateteachers.



The First InventorHe was a clever old priest, one Dean

Herbert, who lived at the end of the twelfthcentury.

By the custom of the time, all corngrowers had to take their grain to the chieflandlord's mill to be ground, which wasexpensive, and involved much unnecessarytransport; in a few exceptional casestenants were forced to convey the grain asfar as fifteen miles.

Dean Herbert thought out the idea of awindmill, and employed a carpenter tobuild it for him. It worked very well.But when his landlord, a certain AbbotSamson, of Bury St. Edmunds, learned ofit, he forthwith destroyed the mill on theground that it interfered with the trade ofhis own watermill !

It was nearly a hundred years beforewindmills became common in England, andthough none of these early structuresexist to -day, we have sketches of them inold missals, and carvings in churches.

From this we know that the first wind-mill was a small wooden building, like alarge dog kennel, placed upon a centralpeg or post ; hence the name " peg mill."The disadvantages of this type were verygreat, winds changed constantly, andwhen this happened the miller had toturn the whole structure round by pushing

This article deals with numerous difficulties encountered by inventors in the developmentof the windmill, and also the ingenious mechanisms employed for grinding corn.

THE discovery of the water -wheel wasthe first, and most important, of thelong series of inventions by which

man has harnessed mechanical power tosave himself from daily toil. But the useof the watermill was obviously restrictedto places where rivers and streams of suffi-cient size and speed were available-sincetide -mills have only rarely been used.

Thus in low-lying countries like Holland,though rivers are abundant, their flow istoo sluggish to drive a mill ; and in many ofthe drier countries there are no streams atall, except in winter.

Even in our own well -watered country,there are considerable areas where the riversare too sluggish, too small, or too few, todrive the mills which were needed in manycentres of population.

That is why we see windmills gracing thelandscape through the vast lowlands ofEast Anglia, North-west Lancashire andEssex ; as well as in hilly districts, suchas the Weald of Kent and Sussex, thehighlands of the Midlands, and many otherdistricts.

The invention and development of thewindmill makes a very interesting story ofpractical mechanical progress, and provesthat the earliest inventors had the same, orgreater difficulties, as have been encoun-

tered in more modern times.It shows also the fact that thefirst forms of this great dis-covery were crude and ineffi-cient, and required the work ofmany clever brains to bring the

idea to perfection.

(Above) A remarkable eight -sailed tower mill at Heck-ington, Lincs., and (right)the turret -post Mill, nearKing's Lynn, Norfolk. Thismill revolves on a centralpeg, held in a concreteturret, and the structurebeneath serves as a store

for grcin and flour.

on a long pole. This not only involvedmuch heavy labour, but also risk ofdamage to the mill if the change werenot made quickly enough.

Danger of High WindsThere was also the constant peril that

the mill might " run away " in highwinds, in which case the sails might betorn off,. or the mill itself set on fire bythe tremendous friction. At such timesthe miller's only chance of saving his pro-perty was to summon all the help he could,and keep the stones, or sets of stones,constantly supplied with grain. He couldthen do a month's work in a single day,and as long as the stones were grinding,the mill could not " run away."



A three-quarter smock mill at West Chiltington,Sussex, so called because the wooden casing goesover the mill like a smock for three-quarters of

the height of the tower.

But the brains of the inventor soondiscovered improvements. The first wasto the sails, which originally were of tarredcanvas, and so offered exactly the sameresistant surface to a gentle breeze, and ahundred -mile gale. The slatted sail over-came this difficulty, as it was constructedof slats like a venetian blind. When thewind was moderate the slats were closedand offered full resistance to the breeze,but as it increased the slats graduallyopened, and so let the excess power passharmlessly by.

Brakes, too, were introduced to check thespeed of the mill, but this was only a partialsafeguard, as in great gales even the frictionof the brakes might fire the mill.

The most important improvement wasautomatic gearing, by which the sweepsof the mill were always kept exactly in thewind, without any attention from themiller.

Automatic GearingAt first this was effected by means of a

flat vane, like the rudder of an aeroplane-which pointed in the direction of the windlike a weather -cork. and as the sails wereat the correct angle t3 the vane, they weremoved round as the wind changed. Butthis arrangement could only work withquite small mills (it is still used with thesmall circular modern mills) and the largermills required a vane unmanageably large.This difficulty was overcome by a clevermechanical idea. A small wheel wasfurnished with sails, and set at right anglesto the sweeps of the mill. It was so adjustedthat when the main sails of the mill werecorrectly set to the wind and revolving, theadjusting vane was edgeways to the wind,and was out of action.

If, however, the wind changed,they started to revolve, and bymeans of a chain of gear wheelsbrought the mighty sails back intothe wind. But there remainedstill another important improve-ment, which was the idea of aclever Dutchman. He fixed thesails of the mill to a

conical cap, so that it alone revolved to carrythe sails into the wind, while the mill itselfstood still.

This enormously reduced the labour-human or mechanical-required to turnthe mill, and also made it possible to erectthe mill of permanent materials, such asstone or brick, and far larger than hereto-fore. It is to this invention we owe the sky-scrapers of milling, such as the gigantic millat Yarmouth, with a brick tower 120 feethigh, and the splendid eight -sailed mill atHeckington, in Lincolnshire. There arealso some fine examples abroad, notablythe giant mill on a hillock in the centre ofLeyden (Holland), and another at Reykjavik(Iceland).

Small MillsAll modern mills up to about forty years

ago were built on this principle ; that is,

(Above) A towermill which is

hand operatedfor changes inthe wind, atBarbados. Thesails are movedround by a longpole. As thetrade winds inBarbados blowsteadily in thesame directionfor nine monthsin the year. ithas not beennecessary to fitautomatic gear-ing; and (right)a modem cir-cular mill atwork in British

West Indies.

brick tower, movable cap, andautomatic gearing, but since thenwindmills have gone out offashion for grinding corn. Thereis a fine windmill at Stretham,near Ely, which was built in1880 and is still working. Itclaims to be the last of its typeto be erected in this country, butin various districts there are

(Right) In windmill land. A scene nearSchemerhoom. Holland.

A smock mill at Shipley, Sussex.

many hundreds of these fine old veteransstill busily working.

In more recent years only smaller millshave been built, but these are in regularuse at home and abroad. They are builtfor cheapness, simplicity of construction,and ease' of erection.

The tower is open ironwork of the latticepattern, the sails are circular and slatted,and there is a vane which keeps the sailsto the wind. The power impulse is con-veyed by a long rod, working like a pump -handle. Such mills are light, inexpensive,and easy to erect, and so are widely usedfor pumping water, cutting mangels, andother light power purposes on smallholdings.

Although one of the earliest forms ofnatural power, the windmill is still per-forming useful work, particularly in districtswhere a natural head of water does notsupply an alternative and more satisfactoryform of power. Houses remote from townelectricity undertakings often use a smallwindmill for driving the dynamo of smallhouse -lighting plants. Under the gridscheme, it is likely that this final connectionwith a picturesque and one of the earliestforms of power will vanish.



HOME-MADERELAYS

An efficient and easily made piece of apparatus that can beconstructed from an ordinary electric bell.

THE object of a relay is to put intoaction (by means of a small current) acurrent of any magnitude in another

circuit, and, for a very small outlay oftime and money, such a relay may be con-structed from an old electric bell, which,if not already possessed, can be purchasedsecond-hand for a very small cost. Aselectric bells vary in size and shape, it is,of course, impossible in this article to giveexact dimensions of most of the parts of therelay, but the accompanying diagrams willindicate to the reader the general lay -out,and very little ingenuity will be required toadapt the plan to his own particular bell.

The Electric Bell UsedFig. 1 shows the most usual type of

electric bell, which has a trembler and a" make -and -break " C. Remove the gongS, the hammer T, the wire which connects Cand one terminal A, and the wire whichconnects B to the arm E. Do not removethe " make -and -break " screw from thebase, as this will serve later as an adjust-ment-although it will no longer be inelectrical contact with the rest of theapparatus. Connect the end B of the wirefrom the coils to the terminal A. Theaction of the bell is now that of a " striker."At this stage a battery should be attachedto P and A, and if the work up to thispoint has been carried out efficiently, thearm E should be seen to move slightlytowards the coils. If this is so, disconnectthe battery.

The InsulatorNext obtain a thin strip of brass about

SECONDARY

2 in. long and in. wide.Near to one end drill a holeto allow a metal screw F topass through it easily. Thisscrew is secured in position by a lock nuton each side of D. Cut out a small insulatorR from a piece of vulcanite or other similarmaterial and screw it on to the end of F,being careful that the screw does not pass

SECONDARY

Fig. 3.-A per-spective sketchof the finished relay.

the job is much neater if thewires are run on the under-

side of the baseboard in the usual manner.The Adjustments Necessary

There are several adjustments to therelay which will allow it to be set so that

its sensitivity may be great orsmall. The old " make - and -break " screw C, which is usuallyfixed with a locking screw, willenable the beam E to be set atvarying distances from the coils.The screw F may be set in anyposition by the locking nuts, sothat there is a suitable pressureon 0, and the rods passingthrough H and K will allow ofsuch fine adjustment that theslightest movement of E will besufficient to close the circuit inthe current when the relay isactuating.How to use the Relay

To use the relay, connect theterminals A and P to the in-coming, or primary, circuit, andthe outgoing, or secondary, cir-cuit to the terminal M and toeither L or N, as required. Whenthe circuit in the primary is com-pleted, the beam E is attractedtowards the coils. This causes Dto move the contact G. If thesecondary circuit is connected toM and L, the gap betweenand H is closed, and the secon-

dary circuit is completed (Fig. 4). Therelay can thus be used for, say, an extensiontelephone call -bell. If the secondary circuitis connected to M and N, while the primarycircuit is complete the contact G will bepushed away from K, but if the primarycircuit is interrupted the gap between Gand K will be closed, and the secondarycircuit will be completed (Fig. 5), as in aburglar alarm. So one end of the secondarycircuit is always connected to M, and ifthe other end is connected to L the relaywill work in the " on " position, but if theother end is connected to N the relay willwork in the " off " position.Quite Simplified

Although the construction of this relaymay at first sight appear to be complicated,the time taken to carry out the actual workis very little more than that taken to readabout it, and the cost of the materials isalmost negligible, as almost all of them canusually be found in the " junk -box " of theaverage amateur constructor.

L M

Fig. 1.-The most usual type of Fig. 2.-Showing the bell andelectric bell which has a trembler hammer removed and the vari-

and a" make -and -break." ous alterations necessary toconvert the bell into the relay.

Fig. 4.-Details of the secon- Fig. 5.-Sketch showingdary circuit, showing the corn- method of operation.

plete wiring.

completely through the insulator.Remove the arm E and fix the brassstrip D to E by means of small screws,filing the ends of the latter flush withthe surface of E, and then replace Ein its original position.

consists of a piece of brass foilabout TA 0 in. in thickness, wellhammered to make it tough andelastic. This foil must not be verythick or it will resist the movementof the relay and decrease its sensi-tivity. Cut 0 in the form of a rect-angle and bend back a strip of itlengthwise at right angles, so that itcan be fixed in an upright position bysmall screws in the baseboard. Ata distance of about it in. on eachside of 0 fix a battery terminal(No. 65) of the pattern shown inFig. 3, and through each pass a pieceof 4 -in. brass rod, the contact endhaving been turned or filed to a point.

Final Wiring and AdjustmentFix to the base three terminals L,

M and N, and connect L to H, Mto 0, using a small waster under thescrew in 0 to make a good contactwith the wire, and N to K. In thediagrams the wiring is shown on the

the top of the baseboard. If strappingis used, this is to be preferred, but ifordinary copper -covered wire is used

PRACTICAL TELEVISION6d. Monthly.

Special Article by J. L. BAIRD.All the Latest News about the new hobby.

Lavishly Illustrated.Published by GEO. NEWNES, LTD.,

8-11 Southampton Street, Strand, W.C.2


304 NEWNES PRACTICAL MECHANICS

The Townend RingTHE Townend ring around a motor

increases the speed of the plane,because it actually pulls the ma-

chine ahead during flight. If the ringwere placed in a slipstream by itself,it would blow backward ; but when itis placed around the motor it pullsahead. The explanation lies in thefact that the metal ring is really alifting surface with a cross sectionsimilar to an aeroplane's wing. Thefront of the ring has a smaller diameterthan the rear, so the effect is that of havinga lifting surface all around the motor,which is tilted forward. The air currents,hitting the flat surface of the motor, aredeflected radially and strike the ring atsuch an angle that the resulting lift isforward. The stronger the currents, thegreater the forward lift or pull exerted bythe ring (Fig. 3).

SlipstreamsContrary to common belief, the slip-

stream or blast, sent back by the propeller,does not spread out behind the whirlingblades. Instead, it contracts, or funnels -in, behind the tips, so that the diameter ofthe slipstream is less than the diameter ofthe propeller. As the blades suck air fromthe front, other air rushes in from all sidesto fill the hole. Thus it is drawn in froman area of greater diameter than the circleof the blades, and this side air, coming inat an angle, compresses the other air towardsthe centre of the slipstream. Strings tiedto the frame of an electric fan illustratethis as they fly at an angle to the centre ofthe draught (Fig. 2).

Streamlining.If you have ever shot an orange seed

across a room by squeezing the pointedend, you have demonstrated why the bodyof a gull is better streamlined than that of adragon fly. In a stubby, streamlined body,like a gull's, the bulging forward partdeflects the air currents outward so thatthey come back, squeezing together near the

t

otti

OfuniceSEED fl /TNSAME BL eiN

rear at two miles a minute outside, thereA/R re.,Q,etwrs is usually a draught blowing forward/DRESS 7226.e.r/v4--,,e against the wind. The explanation is

//EREthat the airstream is deflected by thefat part of the streamlined fuselage,just behind the nose, so a suction isformed, similar to that which giveslift to the top of the wing. Fartherback, these air currents press down

,079,460N /42 W again against the sides of the fuselage.Thus the suction in front and the pres-sure behind pump the air forward in an

opposite direction to that in which theplane is travelling (Fig. 1).

AV COP/PEA/TS/049gss TOGETHER,14-.PEXA/17441ERTRae, ON &RDFROM

40/w/v6.4s6ort

/44/EN .5-71JeszEo47--)7,/,4,0,0 ENO.

Fig. 1.-Illustrating that a gull's body is better stream-lined than that of a dragon fly.

rear. In the long "darn-ing - needle " body ofa dragon fly, the aircurrents come togethernearer the head. Thesame principle holdstrue in aeroplanes.

Draught in an Aero-plane Cabin BlowsForwardIn the cabin of an

aeroplane, although agale rushes past to the

Z2/4mEre,e OF ,f2x0.5-7,E,E,44f / LESSTHAN OF Acezotz L Eye

The Pressure on the Front Spar of the WingDuring trial runs at top speed, the wings

of a number of early planes broke down-ward in the air. The cause was a mystery,until tests revealed that when high-speedplanes fly all out, the pressure on the frontspar of the wings is often downward. Atpeak speeds, powerful planes, with lightlyloaded wings, fly with the leading edge ofthe wing lower than the trailing edge. Mostwings will lift at a negative angle of from 2to 6 degrees. In this position, the wing isstruck by the head-on wind on the topsome distance back from the trailing edge.This pushes down the forward part of thewing and shifts the partial vacuum areaback toward the rear spar. Consequently,at great speeds, the pressure on the frontspar is actually down instead of up (Fig. 5).

In Aviation 1 lb. equals 21 oz.For every pound added to the carrying

capacity of an aeroplane, they must add5 oz. to the weight of the structure tomake it strong enough and large enough tocarry the extra load. A little bigger wingis needed to support the extra pounds, abigger engine to push the larger wingthrough the air, added petrol to feed thelarger motor, bigger fuel tanks to hold theextra petrol. Consequently, when thecarrying capacity of an aeroplane isincreased 1 lb., the added load it must liftinto the air will be, not 16 oz., but 21 oz.Inversely, cutting the weight of the machine1 lb. saves 1 lb. (Fig. 7).

Two and Two equal Six in AviationIf two streamlined struts, each having

2 -lb. resistance in passing through the air,are placed near together, their combinedresistance will not be 4 lb. It will some.times be6 lb. ormore. Thereason is theair flowaround onestrut inter-feres with

Fig. 2.-The slipstream sent back by thepropeller does not spread out behind thewhirling blade. (Right) Strings tied toan electric fan fly at an angle to the

centre of the draught.

..P722/NGSONELEC772/C/CANCO/YPEROE70- 14,417.0CEN7-..2E



the air currents passing around the other.Eddies are formed between the two, thusincreasing the drag. Planes with twinbodies or closely placed hulls have oftenproved inefficient due to such interferencedrag. Designers try to keep wings, strutsand fuselages from interfering with eachother as much as possible. In fact, a honey-comb radiator produces more resistancethan a flat surface of the same area, becauseeach little tube produces interference.

A Falling Plane would pass a Falling BodyIf a stunt man, making a delayed para-

chute leap, jumped from a plane high in theair, the pilot, diving with the engine cutoff, could drop faster than the jumper. Onboth subjects the pull of gravity would bethe same, but the falling man would notbe streamlined, while the plane would be.Consequently the aeroplane, with lessresistance in proportion to its weight,would travel faster with the same pull ofgravity.-(Popular Science.)

Airway and Aerodrome Lighting

AY6 POLLSFo,eiv,4,eo

OA-:ZAcT " 0/Yoe/HG

4/.2.4-0/L.In his paper on " Recent Developments far apart. British practice was compared

Iin the Lighting of Airways and Aero- with that abroad, and it was shown that wethemes " at a London meeting of the allow much 'more light for bad weather

condition and incline to lower/0-4,277,4L ace/o/Pf 4r beam intensities and rapidf,PoNTC2A-C,46/A/ Slices signal repetition. The advan-a,v5hoz- 44E, /52#9,4,42,0 tages of beacons giving over

a million candles in the main

Peo,0ELLER POLLS/.7L-4/ve FoAn-v.4,eo

/PES/STANCE OFPLANE" /0L/LLS//Y OPPOSITE.0/47EcrioN

Fig. 3.-The Townend ring around the motor actually pulls the planeahead during flight.

Fig. 4.-This diagram shows why thedraught in an aeroplane cabin blows

forward.

Yik/eEz//va:41.?Co.avEivrs 47 -,PEAR,1/W,,i7e/Na 7Mecuad/

/E4frS //v/zart-z,46-E,Po..r/644 fax=ww.ez7

Illuminating Engineering Society on March12th, Mr. H. N. Green stated that thedesign of aviation lighting equipment hasreached a stage when it is more difficult tostate the requirements of lighting than to

beam were questioned andthe performance of sucha beacon in bad visibilityconditions was analysed.

LA/vONvG GYRESR4c4--,es ss-0,1/h-7743-

Zik;t2A--e- /;eo .0omyA',E,EsscheE 0/v

frI,/s/as

build apparatus to meet the requirements.His paper was mainly devoted to a descrip-tion of recent developments in our know-ledge of requirements, starting with a briefreview of the visibility of light signals,covering threshold illumination, the prac-tical threshold for recognition of a signal,fovea] and paraveal vision, the effects ofbackground brightness and of a flashingcharacter. After explaining the principleof spacing airway beacons along a route,the author showed that low -power beaconsclose together mark a route less effectivelythan high -power beacons placed relatively

A New Type of BeaconThe latest design of beacon installed on

the Croydon-Lympne airway was describedby the author. An interesting feature wasthat two beams of light are emitted andtwo separate lenses are used to produce eachbeam ; the inner lenses controlling thehorizontal divergence, while the outerlenses give the required vertical distribu-tion. By this arrangement the resultant

PARACHUTErsr STUNT 414N

',:1111 I I / f-

S.

/LANEDiv/n/640w/Woro,e ack-

C

Fig. 6.-An aeroplane wouldfall more quickly than a falling

body.

iljr J

IJ Sr,aciAiL/NEDP..44/vt; fr147-NZErs

rivREAS m/St/TASfpFEe;PE14/42/21/0 zei z2ND

beam has the/Celisame horizontalFAST1-ioriEz12ontal divergenceat all angles of elevation, and consequentlythe duration of the flash exhibited is thesame for any direction of observation.An oscillating beacon which exhibits adefinite " on course " signal was alsodescribed. Although Neon light is still usedfor aerodrome beacons, the author main-tained that it has no special fog -penetrating

APESSCAQE /s Down/ AT ///6H14/NEN LEA,opyG EDGE

LNG /s Loki/ER 77/4/Y7-PA/Li/VG E.OGE

Ookoeheo PREsseh2e ONF0.214/42O Gt/v6.. ,570,4,247Zoi-vSPee'os

Fig. 5.-Showing the direction of pressure on the front spar of a wing when the aeroplane is travellingat a high speed.



qualities. It was scattered and absorbedby the atmosphere in just the same way asany other red light, and, with visibilitydown to a mile or less, a Neon light couldnot be seen appreciably further than awhite light of equal intensity.

Blind FlyingBlind flying, in the future, might neces-

sitate the use of a more powerful aerodromebeacon than the Neon type. A pilot comingout of the clouds, somewhere in the vicinity

of the aerodrome and with ground visibilitypoor, had no idea of the direction in whichto look for the beacon, which must bepicked out from other red signs by its flashperiod. It was therefore possible that alight which was recognisable by virtue ofboth intensity and character might in timebecome preferable to one which isrecognisable by character alone.

Aerodrome Floodlights for Night LandingThe best and most convenient-and

<-)Uu.VuED co n o D (,

(-° 61=1 C,

tDC.)e) CC)

>-

1/0/YEYCOM9/i7/1.0/A TOR

0/3PODUCES /110,PE/PESYSTANCE 71 -/ANSOL/L2 SURFACEOF THE SAMEAREA

____----------

EW44:00;/CIAPRENTS

-----

--30.-d

41W EDDY elhOPENTS BEEDTfrvo.57-,par.3- PLACE!, Czost-

To6Er,,,,ER //vc,c7z4sh- //e.,ho2/3S ResisrANcE APES/STANCE

1.3111.

/f7E.S/STAHCj.-...-/r

Fig. 8. - Planeswith twin bodies onclosely placed hullshave often provedinefficient, due tointerference drag,

as shown here.

Fig. 7.-In aviationone pound equals

twenty-one ounces.

V/AT/O/V,80/30WTH EXTA14a/ nicks. A

NORMALAVN0 TOTAL OE .2/OF / 6 OUNCES OUNCES

incidentally the most expensive-is to instala number of fixed floodlights at intervalsround the aerodrome boundary. One ormore floodlights could be turned on,according to the direction of the wind, andas the whole installation could be remotelycontrolled, there need be no delay inbringing the lighting into action, or followingchanges in wind direction. The authordescribed some interesting floodlightingdevelopments in Germany and Holland,dioptric floodlight-with lamps with fila-ments shaped to increase the maximumluminous intensity, and reduce the fore-ground illumination. Figures were givenshowing the improvement in floodlightingperformance during recent years. Thelatest designs of boundary lights used inGreat Britain and Germany were described,and the use of sodium tubes in Holland wasreferred to. The light distribution of obstruc-tion and boundary lights was also referred to.

MORE than 2,500,000 miles wereflown by the air -liners of ImperialAirways during 1934. This figure,

which has just become available, compareswith approximately 2,300,000 miles for1933. The progress of air transport isillustrated, strikingly. if one contrasts thestatistics of our present-day air -mails withthose of the first officially sanctioned aero-plane mail to be flown in England, thetwenty-fifth anniversary of which is to becelebrated this summer. That pioneerHendon -Windsor service of 1911 operatedover a distance of only 20 miles, comparedwith the 20,000 miles of route flown overby Imperial Airways and its associatedcompanies at the present time. The'planes in use on that first service weredriven by single engines of 50 h.p., and hada wing span of not more than 28 or 30 feet.To -day the big mail -planes are driven byfour engines, developing a total of morethan 2,000 h.p., and have a wing span of130 ft. As for a comparison of the loadscarried by air, then and now, the mono-plane which actually inaugurated theHendon -Windsor air -mail of 1911 carriedjust its pilot, Mr. Gustav Hamel, and abag of letters weighing 231 lb., whereasone of the big four -motored air -liners ofto -day will lift into the air a useful load ofjust over three tons.

A Difference in SpeedAs for the vital aspect of speed, whereas

the first mail -carrying 'planes flew at fromforty to fifty miles an hour, the four-engined aircraft of to -day, even whencarrying considerable mail loads, canattain a speed of 175 miles an hour.

THE AIR -MAIL OF 1911 COM-PARED WITH THAT OF 1935

A study of the latest air traffic figuresshows an increase of more than 20 per cent.,recently, in freight dispatched by air fromLondon to the Continent. And this aug-ments the general story of progress, asrevealed by current statistics for passengersand mails. Three of the main air routes tothe Continent - London -Paris, London -Brussels and London-Germany-are allshowing a substantial air -freight growth ascompared with previous figures.

On the Imperial Airways line to Paristhey have been having exceptionally largeconsignments of wireless apparatus recently,while on the service to Brussels a trafficfeature just lately has been a continuedincrease in the quantity of wireless valvesconsigned by air. For delicate articles likethese, the advantages of air transport, withits absence of jolting or vibration, are sogreat that the bulk of such goods are nowbeing sent by air, the valves requiring nospecial packing, but travelling quite safelyin ordinary cardboard containers.

The same applies to electrical appliances,scientific instruments, and fragile goods ofall kinds. Handling is reduced to a mini-mum ; and though speed naturally costsmoney in the air, as on land and sea,consignors reap a very considerable advan-tage from the fact that insurance rates forgoods by air are, generally speaking, onlyabout one-third those for surface trans-port ; while packing costs are also reduced.

Heavy ConsignmentsThe big air -liners in use to -day, and the

roomy cargo spaces now available, enablefreight consignments of a size and weightto be dealt with which it would havebeen impossible to handle not so longago.

On a route to Germany, for example, apiece of machinery weighing over half a tonwas air -borne recently, while not long agoa 'plane had among its cargo a small motorcar. Motor cycles, urgently required onthe Continent, are often dispatched byair, as are spare parts of all kinds formotor cars-these last-mentioned not onlygoing over to the Continent, but beingdispatched for thousands of miles along ourEmpire routes.

Should they prove too bulky for dispatchas a single unit, mechanical parts can, as arule, be divided up into several separateconsignments for air transit. In this waysuch things as urgently required drillingmachinery, pump fittings and engine partsare carried by the Imperial Airways' ser-vices to points along the Africa and Indiaroutes, saving many days, and often weeks,as compared with surface transport.

Increase in Passenger ServiceIn addition to freight progress, passenger

and mail traffic by air continues to increasesubstantially. During the past twelvemonths more than 50,000 travellers flew inand out of Croydon in the aircraft ofImperial Airways, while the mail loads sentby air from this country during 1934 wereby far the largest ever recorded, totallingapproximately 6,000,000 letters.



Fig. 1.-Indicating how the whole of the interior of the spot -lightstudio is completely lined with copper sheet to prevent radio -frequency

interference.

LAST month two specific methods forproducing the ordered scanning linerequirements were dealt with in a

general manner, so it is now necessary togive further details concerning the prac-tical applications of these principles.Dealing first of all with the spot -lightmethod of television, the initial require-ment is a very intense source of light, andthe most suitable arrangement is to use ahigh-powered arc lamp which is being ratedat 150 to 200 amperes consumption. It hasan automatic feed and is mounted on arigid iron framework. In front of this, inthe same projector room, is the largediameter scanning disc housed in a largebraced casing from which the air is pumpedcontinuously to maintain a reasonabledegree of vacuum. The disc in this wayruns truer, while there is less likelihood ofthe small scanning apertures becomingclogged, ' wholly or partially, with smalldust particles and so spoiling the field oflight. Any dirty hole gives a black hori-zontal line on the final picture, and this hasto be guarded against in achieving the bestresults.

In the StudioAs shown in Fig. 3 of last month's issue

the light from this arc lamp is made to fillthe mask cut out, and in this way, togetherwith the associated focusing lenses, a tinymoving beam of light is made to emergefrom the final lens. A thick wall separatesthe projector room from the studio proper,and to allow a free passage for the scanningbeam an aperture is let into the wall, thisbeing sealed with thick plate glass. Thisis seen in Fig. 1, and no background noisecan thus mar the acoustics of the studio,and be picked up by the microphone seennear the left-hand photo -electric cell inFig. 2.

The subject being televised stands2 or 3 ft. away from this wall aperture,and interposed between him and thedividing wall is a large framework accom-modating five photo -electric cells. As willbe gathered by referring to Fig. 2, these arevery large, being housed in metal oases with

TELEVISIONMADE EASYBy H. J. BARTON CHAPPLE, Wh.Sch., B.Sc., A.M.I.E.E.

The second article of the series. This month we deal withthe spot -light method of television.

a wire mesh front, whileassociated with these cells arethe " A " or first stage ampli-fiers. They are arranged insuch a manner that they canbe influenced by the greatestamount of light reflected fromthe rapidly moving scanningspot as it explores the televisedsubject, natural high lights anddepth being imparted to thehuman features by carefullypositioning these cells.

Instant by instant duringthe continuous scanning pro-cess the cells " pick-up " the

varying reflected light, and owing to theirinherent photo -electric property the lightchanges are made to produce a correspond-ing voltage change in an electrical circuitin which these cells form a part. In spiteof the large electrode surfaces the voltagesignals are small in magnitude and requireconsiderable amplification, but they repre-sent a faithful replica in voltage amplitudeof the degrees of light and shade con-stituting the subject being explored. Afterthe final amplifiers the signals are fed toa central control before being passedto the radio transmitter to become amodulated electro-magnetic carrier wavein space.

IsolationEvery precaution must be taken in the

studio to ensure that it is free from anyform of high -frequency interference, andthis is carried into effect by completelylining the whole studio interior with sheetcopper. This is shown in Fig. 1, the thicksound -proof door being treated in the sameway so that it makes a proper electricalcontact when closed, the screening beingeffectively earthed. The walls are thenpadded and draped to produce the correctacoustics, the microphone picking up thespeech, song or music which accompaniesthe " turn " being performed.

At the same time as the vision and soundsignals are being generated, the scanningmechanism has associated with it apparatusfor the purpose of producing both high- andlow -frequency synchronising signals. Theformer corresponds to the scanning linesequence per second (240 x 25 = 6,000pulses per second in the proposed highdefinition service), while the latter is thepicture repetition frequency now stand-ardised as 25 per second for high definitionwork. To give twenty-five pictures persecond (and so eliminate any trace offlicker in the final received picture, and alsoallow artist movement to be reproducedquite naturally in the observed image) thedisc has to rotate at a speed of 1,500 revolu-

Fig. 2.-Showing the interior of the spot -light studio, with the dividing wall aperture and bank of photo-electric cells surrounding the subject to be televised.



tions per minute for a single spiral trace ofscanning holes. It is also possible to havea double spiral trace of holes, each spiralhaving half the total number of holes andso being separated by twice the angulardistance, and rotate this disc at a speed of3,000 revolutions per minute. When this isdone, however, two holes would normally

CAMERA(INTERMITTENT)

FILM SPOOL

picture has been dissected is twice the totaldisc apertures, which in the examplequoted is 2 x 120 = 240 lines. Thearrangement of relative motion has in thisway given the scanning conditions required.

At any and every instant of the holemovement, the amount of film picture lightexposed by the hole passes right throughthe disc and " falls " on the active electrodesurface of a single photo -electric cell posi-tioned accurately for this purpose. Everyelemental area of film picture light andshade is thus converted by the cell to anequivalent voltage amplitude in the circuitof which it forms a part. This continuouslyvarying signal so generated is amplified andpassed to the control room for subsequenthandling by the radio transmitter in thesame way as the spot -light television signal.

DEVELOPER FIXING & WASHING

appear simultaneously owing to thedouble turn spiral, and a gearedchopper has to be included in themechanism to mask off the holewhich at that instant should not bescanning, and so let each hole do, itswork in turn.

Televising Talking FilmsComing now to the tele-cine projector for

producing television signals from standardtalking films, a view of one of the Bairdmachines was given in Fig. 8 of last month'sissue. This should be studied in conjunctionwith Fig. 3, which shows the bare essentialsin simple pictorial fashion. A bright lightsource (in this case an arc lamp) fitted to theleft of the projector machine has its beamof light focused on to a rectangular gatethrough which is driven the film by gearedsprockets. No shutter mechanism is in-cluded in the equipment so that the result-ant effect emerging from the secondfocusing lens is a series of still picturesmoving downwards across a slot in ametal mask, one after the other, at a rateof twenty-five pictures per second.

Instead of " throwing these pictures onto a screen they are focused on to the top -rim of a scanning disc, which, for a 240 -linepicture, has a series of 120 minute holeslocated on a circular trace with an angularseparation of three degrees. The disc isrevolved at 3.000 revolutions per minute andeach separate hole traces the same arc path(regarded as a straight horizontal line for allpractical purposes) during the running ofthe disc. The width of the projected filmpictures at the top of the disc is such thatonly one hole at a time is accommodatedduring the scanning process.

Double MotionAs the picture moves downwards at a

constant speed, the disc holes move acrossat a constant speed, and although each holetraces the same path as every other hole,due to the downward movement of the filmpictures, the line traced across by each holeis a hole width separated from its immediateneighbour. One complete film picturemoves down the mask slot in one twenty-fifth of a second, but during that time thedisc has made two complete revolutions, andhence the number of lines into which the

RE. CELL

1.TO RADIO TRANSMITTER

'.

CONTINUOUSSCANNING

FILM

COLLECTI NG

TANK

LAMP

Fig. 3.-Showing how the intermediate film processworks.

While the television signals are beinggenerated, the film passes through thestandard type of talking film head. Herethe sound recorded on the narrow filmtrack between the sprocket holes and filmedge by either the variable density orvariable amplitude method is convertedto an electrical signal through the mediumof a small projectionlamp and photo-electrical cell. In addi-tion, associated withthe picture scanningmechanism are doublesynchronising fre-quency pulse genera-tors to give both theL.F. and H.F. signalsrequired at the receiv-ing end, as we shall seelater on in the series.

A Form of DelayedTelevision

Since it employsidentical methods ofscanning as that usedby the tele-tinemachine, it is appro-priate at this junctureto deal with yetanother method forproducing televisionpictures. This is theBaird intermediate filmapparatus, a simplepictorial sketch of which is shown in Fig. 3.Using 17.5 mm. film a special camera takespictures of the scene to be televised in a man-ner similar to an ordinary cinematographcamera. Both indoor and outdoor scenes canbe photographed, and, as an example of thelatter, reference can be made to Fig. 4,which shows part of the equipment usedwhile " shots " are being recorded of horsesexercising in the Crystal Palace grounds.

After leaving the camera (an intermittenttype) the film is fed through a series oftanks by sprocket wheels and rollers. Inthese tanks there are the appropriate photo-graphic developers and fixing solutions, andafter going through this process the film iswashed. While still wet, the film nowpasses down through a " gate," on one sideof which is an arc lamp and on the otherside focusing lenses and an encasedscanning disc, where the projected filmpictures, moving in an uninterrupted path,are scanned by a circle trace of minuteapertures in exactly the same way as thetele-tine apparatus just dealt with.

ApplicationsIn addition, a sound -recording tube makes

a variable density sound track down thefilm edge to be " taken off " at the otherend of the film journey through the tanksas a sound signal. Finally, the doublesynchronising pulses are also generated asin the case of the tele-cine machine. Theremarkable feature of the whole apparatus,however, is that the time which elapsesbetween the photographing of the scene onto the film by the camera and its dissectioninto a " multi -lined " television imagesignal from the finished but wet film nega-tive is only about half a minute.

This has only been made possible by acareful study of photographic and develop-ing technique, but it enables the machineto be used for a wide variety of purposes.Accommodated on a lorry it can producetelevision pictures of any outdoor event ofsporting or national interest, while indoorstudio plays, sketches and so on all comewithin its scope. Not only can the trans-mission of these signals be effected with adelay measured in seconds, but the event,no matter of what nature, is stored in cellu-loid form for subsequent transmission atany other time when such a course is deemeddesirable.

These three methods of producing tele-vision pictures for any public service, andusing mechanical scanning, have been

Fig. 4.-Using the intermediate film high -definition scanner to televise anopen-air scene of horses at jumping practice.

developed to a high degree of efficiency,but there is yet another important schemefor performing similar functions and whicheliminates all forms of mechanical scanning.This is the electronic camera which is nowbeing investigated and improved to takeits place in the whole arrangements whichultimately will provide television for all.This side of the question will be dealt withnext month.



Two types of escala-tor in use at a de-

partmental store.

BROADLYspeaking, apassenger

escalator is amechanism whichcomprises a con-tinuous number Lof steps, whichcan be made to move in a descending orascending direction and which, althoughhaving a step formation on the inclinedportion, gradually changes to flat platformsas the upper and lower fixed landings areapproached.

Escalators are built at a standard angleof 30 degrees from the horizontal, and inthree standard widths-namely, with aninside measurement of 2, 3 or 4 ft. betweenthe balustrading, and operating at a speedof 90 ft. per minute.

There are two types in use for passengerservice ; the flat -step type with smoothtreads, which involves the use of shunts atthe landings ; and the cleat -step type,which is provided with comb -type landings.On the flat -step type, the step appearsfrom under the floor at the lower landingas a moving platform, and as it goes up-ward, it slowly breaks into a perfect seriesof steps, rising into a complete stairway.On each side there is a hand -rail of flexiblematerial, which moves upward at the samespeed as the stairs, thus affording thepassengers a secure support as they ascend.At the top the steps again flatten out intoa moving platform, from which the passengersteps to the stationary landing on the samelevel, with no appreciable sensation otherthan that experienced in walking on thelevel. At the upper landing one of the sidebalustrades turns inward, and the movingplatform disappears under it.

The flat -step type is made either ascend-ing, descending or reversible. The shuntsfor escalators operating in the ascendingdirection are placed at the upper landing ;with the descending escalatorthey are at the lower landing,and with the reversible typethey must be placed at bothupper and lower landings.

The Cleat -step TypeThe principal features of this

type are the use of the perfectstep formation of the flat -steptype, and the use of the comblandings at the top and bottom,so as not to require the space

HOW ANESCALATOR

WORKSThe external appearance and use of theescalator is no doubt familiar to a largeproportion of the travelling public, butvery few understand the internal "mechanism, and this article will there-

fore prove interesting.

on the floors needed for the shunts used onthe flat -step type. The steps are of the

INTERESTING FACTS ABOUTESCALATORS

The following details refer to the installa-tion of eight escalators in various LondonUnderground Stations :-

The combined vertical rise of theescalators was 3,500 ft.

The aggregate of the horse -power of thedriving motors was 6,000.

The number of steps required was over12,300.

The total length of the special step chainneeded was over 32,500 ft.

That of other roller chains used exceeded9,000 ft.

The special moulded wheels which carriedthe steps numbered nearly 50,000.

There were six miles of travelling hand-rail.

same construction as the flat -step type,but have longitudinal cleats screwed to thesteps. so as to permit of the use of the

comb landings. The cleat -step type isalways made reversible so that they canoperate either up or down, dependingupon the traffic conditions ; or it can, ofcourse, always be used in one direction.

Safety DevicesBoth types of escalators are provided

with all necessary safety devices, arrangedto stop the escalator immediately upon anyderangement of the apparatus. They areprovided with full automatic push-buttoncontrol-to start, stop or reverse thedirection of travel. Buttons are con-veniently located at the top and bottomlandings of the escalator. the stop buttonbeing available as an emergency stop ; theother buttons can only be operated bymeans of a key. This prevents the un-authorised use of the buttons and stillmakes it possible for anyone to stop theescalator in case of immediate necessity.

All types of escalators are driven byan electric motor placed underneath thefloor at the top of the incline. Thismotor drives the gears and sprockets, whichin turn operates the driving chain whichcarries the steps.

The Brake DrumA great deal of attention is given to the

design and operation of the main brake,to facilitate the safe -stopping of the esca-

(Above) The escalator machinery chamberand (left) the escalators which are in use

at Holborn station.



The type " L" dear step escalator.

lator under varying loads. This drum,which is roughly 4 ft. in diameter, is actedupon by a pair of balanced shoes lined withferodo and carried by steel arms, spring -applied, and magnetically held in positionwhile the escalator is running. The forceexerted by the brake gear is sufficient to

stop a fully loaded, maximumrise, descending escalatormoving at full speed, but atthe same time it must notstop a lightly loaded descend-ing one so suddenly as tocause undue shock to pas-sengers who may be travel-ling thereon. To do this thebrake magnets, which are ofexceptionally powerful con-struction, and their coils, arefitted with variable dischargepaths controlled by a devicebuilt into the controller, andalso with voltage regulators.

Arrangement of EscalatorsThe arrangement most

generally used in depart-ment stores are the paralleltype and the criss-cross, orbucksaw, each with manymodifications. In all cases,however, they can be ar-ranged for both up and downservice and to give a con-tinuity of travel from oneescalator to another at thevarious floors. The paralleltype has two escalatorsadjacent to each other.This arrangement permitsof taking and deliveringthe up -traffic into the samecross aisle where the trafficconditions warrant such anarrangement. With thecriss-cross or bucksaw type,the up and down traffic iswidely separated, beingtaken away from and dis-charged into separate crossaisles, thereby entirely

separating the up and down traffic, whichin some cases is highly desirable. Undersome conditions a combination of bothsystems works out to advantage.Cleaning the Escalator

The escalator steps are cleaned by a

number of air -nozzles which are directed onto the surfaces of the steps in the vicinityof the lower landing sprockets. The dustand debris are caught in removable trayswhich are daily removed by the stationstaff. The air pressure is about 60 lb. persquare inch and is turned on each morningfor about ten minutes whilst the escalatoris in motion.

The Step ChainThe step chain and wheels are also

cleaned in the same manner, after which afurther set of nozzles sprays them with oil,the air pressure for this latter purposebeing reduced to about 9 lb. per squareinch. The fixed landings at the top andbottom of the escalator are covered withsteel plates filled with rubber flooring andprovided with bronze mouldings. Theseare removable where they cover themachinery, to facilitate the replacement oflarge parts should same be needed at anyfuture time. We are indebted to the OtisElevator Company for the foregoinginformation.

The treads at the turning point at the top of theescalator.

pROGRESS has never before beenswifter than in the last century, whenthe magic of science has wrought such

overwhelming improvements.To look at that now historic little steam

engine " Locomotive No. 1 " is to see thebeginning of the vast railway systems of theworld-the thousands of miles of steelpermanent way-the giant expresses-which to -day we look upon almost as amatter of course.

And yet Stephenson's little engine seemeda miracle to our grandfathers when, as" Active," the first public passenger trainin the world, she attained the modest speedof 15 miles an hour at the opening of theStockton and Darlington Railway in 1825.A huge crowd of nearly 50,000 came togaze awestruck at this unbelievable per-formance, yet now a railway speed of 70miles an hour passes without comment.

The First Man to run a LocomotiveRichard Trevithick was the first man to

run a locomotive, closely followed byBlenkinsopp, and Hedley with his " PuffingBilly," but it was George Stephenson whoset out to improve the locomotive and tolay the foundation stone of the railwaysystem we have to -day.

A WORLD-FAMOUSSTEAM ENGINE

" Locomotive No. 1 " was his thirdexperiment-the first being the " Blucher "(1814) capable of hauling eight loadedwagons at 4 miles per hour, and the secondimproved locomotive was constructed ayear later for the Killingworth Colliery.

" Locomotive No. 1 " was constructed atForth Street Works, Newcastle -on -Tyne,and the model recently made by BassettLowke Ltd. shows clearly its construc-tion.

A Realistic ModelIn the actual engine which weighed

6i tons, the four coupled wheels were4 ft. diameter, and the two vertical cylinders24 -in. stroke, 10 -in. diameter. The waterpressure was 25 lb. to the square inch, andthe tender carried 15 cwt. of coal. After-wards the water barrel on the tender waschanged for the 240 -gallon sheet irontank.

The realistic model made by Bassett-

Lowke measures 3 ft. x 11 in. wide x 23 in.to the top of the chimney, and has beenbuilt to the special scale of in. to the footfor Robert Stephenson & Co., of Darling-ton, from their own old model. It has theunique feature of being a working model.All the overhead motion-the intricate" grasshopper " gear-has been speciallyconstructed for working conditions. Theboiler is of copper with mahogany lagging ;the motion parts are of nickel -plated steel,and the curiously patterned wheels of castiron. The chimney of the model is 16 in.high, and the rails are made in the old stylewith imitation stone sleepers.

An Interesting History" Locomotive No. 1 " itself, as it stands

now on the stone pedestal in Darlingtonstation, has had an interesting history.

For the first twenty-five years it was inservice on the Stockton and DarlingtonRailway, then for seven years as a collierypumping engine.

Since then it has been to Philadelphiaand Paris for exhibitions, led some famousrailway processions, and it came to lifemost appropriately at the railway cen-tenary at Darlington in 1925.


April, 1935 NEWNES PRACTICAL MECHANICS 31I

BUILDING "STREAMLINIAThis month we deal with the woodwork of this fine model speedboat.Previous articles on the construction of this model appeared in our

issues for February and March.

Fig. 2.-The hull in course of construction, showingimaginary chine line.

SINCE our last issue several readers havefound a little difficulty in shaping thehull of Streamlinia, and finding the

correct chine line.A simple method used at Northampton is

shown on the sketch plan reproduced here-with. After marking off and carefullycutting through the profile, working downto the lines on both edges, it will be foundthat the ordinate lines previously markedare cut away. These are marked again onthe top and the bottom of the block, andthe centre line of the hull should now bemarked at both top and bottom of theforward end, preferably with a joiners'marking gauge. The only tools absolutelynecessary for the hull work are a joiner'sparing chisel, a flat paring gauge, both aboutIf in. wide, and a good outside gouge for

hollowing out, but it is advisable also to usea marking gauge if you possess one, as apencil line is so easily erased.

The Chine LineThe outline of the top of the hull is

marked out on the top, and the after bottomoutline on the bottom. To produce thecorrect chine easily, the chine line can be

projected to the bottom of the hull (seeFig. 1, line ABC). On ordinate No. 2, Arepresents the deck outline, B is the chineline, and C the chine line projected to thebottom of the hull. You can mark outthese lines on the body plan. The sketchplan shows projected chine lines on ordi-nates 2, 3, 4 and 5.

In this manner you can start work on theforward end and cut straight through, fromthe top of hull, outline to the projected chineline (see Fig. 2). The elevation of the chineis now marked on the side, and the forwardpart of the hull can be carved in accordancewith the templates of the body plan.

These templates can be very simply madeby placing thin pieces of plywood or card-board under the body plan and prickingwith a needle, afterwards cutting with asharp knife or fretsaw.

In shaping the forward part a good flatgouge will be found to produce the bestresults. It pays to be careful in not takingoff too much at a time, and testing with theappropriate template after each few cuts.

When the forward end is completed, thestern should present little difficulty, andyou can then proceed with the hollowing out.

Hollowing out the HullA skilled craftsman, with the help of tools,

generally takes about three hours to hollowout the hull, but when you are doing thework yourself, it may take up to a week,according to the time at your disposal. Infact, to hollow out the hull a little at a timeis really the ideal way, as naturally morecare is taken over the work. The thinnerthe hull is, the lighter it will be, drawingless water and consequently giving more

Fig. 3 . -(Left). Show-ing the methodof drilling thestern tube. Theoperator isshown sightingthe centre line

of the hull.

Fig. 4.-(R g h t).Shapingthe top ofthe deckhouse on awoodenblock fixedin a ' vice.

speed and better performance. In the caseof Streamlinia, we advise hollowing out toabout f in. thick throughout the whole ofthe hull.

These further facts are given for thebenefit of those who have not yet completedthe hull, but I doubt if many of us, withscoured hulls covered with priming paint,have resisted the temptation to try out ourmasterpieces on water, even if it is in a spotno more adventurous than the bathroom.

A

BOTTOM OFHULL

PROJECTED CHINELINE AT ORDINATE NO:2

Fig. 1.-This sketch shows a simple method ofobtaining the chine line.

I am sure those of us who have done so,have been agreeably surprised at thebuoyancy and modernistic racy " appear-ance of the hull. A good lead paint isnecessary or the wood will be saturated.

Drilling the Stern TubeThe next operation on the hand -carved

hull is drilling the stern tube-not such adifficult job as many would suppose, pro-vided you have the assistance of someonewith a true eye. Place the hull face down-wards on the work table (see Fig. 3). Keepyour eye on the centre line of the hull while



your assistant sights the angle at which youare drilling. It does not matter if the holeis drilled on the large side, as afterwardsthis can be filled in, around the tube, withplastic wood. It is almost impossible todrill a perfectly true hole, and it is certainlypreferable to fit the tube loosely at firstthan to bend it, as often happens when thehole is tight. The hole in the wood blockinside the hull should fit correctly.

Unscrew the gland from the end of thestern tube. Push it through from the out-side, fix the skeg (shaft bracket) with i-in.steel screws (brass screws are liable to breakif screwed tight), and fill in the hole in thehull with plastic wood. Let this drythoroughly before cleaning off. It isadvisable to leave it for twenty-four hours,and in the meantime continue with theupper structure, beginning with the deck,which is best cut from a piece of 5 mm. ply-wood. This can be marked out by placingthe hull on the plywood, pencilling round,and cutting 16- in. outside the line, after-wards carefully cleaning and rounding offwith sandpaper.

The Top DeckhouseNow begin on the construction of the top

deckhouse, and here the fretsaw will befound very useful. On the full-size draw-ings, which can be obtained from Bassett-Lowke Ltd., of Northampton, the deck-house sides are all marked out the actualsize. Otherwise these parts must be scaledup from the drawings reproduced in theMarch issue.

Streamlinia has a white deckhouse, and ifthis is the colour decided on for your model,any hard close -grained wood I in. thick,such as American white wood, would besuitable, but some may prefer a mahoganydeckhouse or some other varnished wood.It is purely a question of taste. Varnishedmahogany is certainly associated with cabincruisers, and it requires very little finishing.

Trace out the deck sides in pencil onwhatever wood you decide upon, with the

grain running along the sides. Use a finefretsaw to cut out the windows, as thenthese will not require so much cleaning.When cutting out these sides, do not forgetthe slot in the after transom for the tiller,as this is most difficult to cut in when thedeckhouse is constructed.

The corner joints must be most carefullymade and fixed with screws and good Scotchglue, or croid, which has reached such

attractive, following the latest principles inaerodynamics, and it greatly adds to thebeautiful lines of the boat.

The roof of the deckhouse is ratherdifficult to hold when shaping, so it isadvisable to screw it down to the bench topat the places where the holes for thepressure gauge or steam valve are later tobe drilled. Or alternatively, it may befixed to a block of wood, held in a carpenter's

Fig. 5.-Showing a side of the deckhouse in the course of construction.

popularity in aeroplane construction. Fig. 5shows the method of fixing these partstogether. The completed deckhouse shouldnow be left for at least twenty-four hours todry, afterwards cleaning up the rough parts,and rounding up the corners smoothly.This streamline deckhouse is certainly most

wood vice. Shape it up with a spoke -shaveand sandpaper to a good smooth finish,ready for painting (see Fig. 4).

Finished unpainted deckhouses may beobtained for Streamlinia from Bassett-Lowke Ltd., for those who prefer this partready made.

Testing the upper air conditions for the guidance of pilots.

SAFEGUARDINGCOMMERCIAL AVIATION

amaz i n gscienti fi c

devices areused by theFord MotorCompany tosafeguard theairways whichradiate fromthe Ford Air-port, at Dear-born, Mich. Awireless beaconflashes its sig-nal, markingan invisiblecourse over theairway, thusmaking it pos-sible for pilotsto fly in dark-ness, fog, orthrough areasof low visi-bility. T h ecourses a r emarked be-tween Detroitand Chicago,and Detroitand Toledo,

0., where one route connects with thetranscontinental airway. Both pilots andstations along these routes are given a half-hourly radio weather broadcast fromstation WQDW at the Ford aerodrome, theweather information being supplied from astation perched high on the roof of one ofthe aerodrome hangers. At twenty-five andfifty-five minutes after each hour, pilots maytune to the station wavelength, and beappraised of the weather at every stationon the routes. Lastly, the small stationwhich houses the wireless beacon trans-mitter at the far end of the aerodrome, isalso equipped with a marker beacon, whichcan be heard at a maximum distance of twomiles. This warns pilots flying in foggyweather, or darkness, of the proximity of theaerodrome, and permits them to find theirway safely into port. The photograph onthe left shows meteorologists of the U.S.Weather Bureau at the Ford aerodromepreparing to test the upper air conditionsfor the guidance of pilots. With the use ofthe hydrogen balloon and the theodolite,the meteorologists are able to measurethe movements of the balloon as it rises,and thus gauge the velocities of the windsaloft. Such information enables pilotsto choose the levels at which they willfly, and to take advantage of favouringwinds.



CHEMICAL EXPERIMENTSWITH SELENIUM

Jons Jakob Berzelius (1779-1848), the great Swedishchemist and analyst and the first discoverer of the

element selenium.

SELENIUM is one of the most interestingof all the elements. It was discoveredas far back as 1817 by that great

Swedish chemist and analyst, Jons JakobBerzelius. Previously, the element, tel-lurium, had been discovered and its namehad been derived from the Latin word,tellus, signifying the earth. Berzelius foundthat his newly -discovered element had manyproperties in common with tellurium.Accordingly, he decided to call his newelement, " selenium," a name which hecoined from the Greek, velene, meaning" the moon." Thus has selenium, even tothis day, been dubbed " the moon element,"although, of course, it has nothing whateverto do with the moon.

As every experimenter knows, selenium'schief claim to fame lies in its extraordin-ary light -sensitivity, a property which wasfirst disclosed by a Mr. May, a telegraphistemployed at the Valentia Island Station ofthe old Trans -Atlantic Cable Service. Theyear of this discovery was 1873. Almostimmediately a number of proposals formaking use of selenium's light -sensitivitywere forthcoming. The first germ of thetechnique of television had arisen in theminds of experimenters. Light-sensitiveselenium cells, however, proved fruitless forpractical television purposes. Neverthe-less, they had and, for that matter, stillhave many important scientific applica-tions. Hence, selenium cells are by nomeans the " back numbers " which fre-quently they are considered to be.

You cannot, of course, purchase seleniumfrom your local druggist or pharmacy.Nevertheless, any firm of wholesale chemistswill be able to supply the material ondemand. The average price is about 2s.per oz. for powdered selenium and a littlemore for the lump variety.

Having obtained it oz. or so of thepowdered or lump selenium, examine itclosely. If the element has been obtainedin lump form, the lumps will be seen to bebrownish -black and glassy -looking, having,here and there, a greenish cast about them.The lumps are brittle and they can easilybe powdered up into a black powder.

Powdered selenium is also black incolour. Some varieties of the element,however, are brick -red in colour. This is a

An Interesting and Practical Article Dealing with the Light-sensitiveProperties of Selenium

different form of the element, and, as weshall see later on, it is the form in whichselenium is precipitated from its solutions.

A Poor Conductor of ElectricityIt is easy to see that selenium is not a

metal. Quite apart from its sensitivity tolight, it is a poor conductor of electricity.As a matter of fact, from a chemical stand-point, selenium is very closely allied tosulphur on the one side and to tellurium onthe other. Now sulphur is obviously a non-metallic element, whilst tellurium is verydecidedly a metal. The properties ofselenium are nearly half -way between thoseof sulphur and tellurium, although notquite half -way between, for selenium is moresimilar to sulphur than it is to tellurium.

Melt a small quantity of selenium at thebottom of a test-tube and note one curiousand well-defined characteristic of the ele-ment. When melted, selenium gives off apeculiar odour which has been described ashaving a resemblance to rotten horse-radish, though, truth to tell, this resem-blance has been much over -stressed. All thesame, selenium does give off this peculiarodour when it is melted in the pure state,and as the odour is by no means a pleasantone, care should be taken not to melt largequantities of the element indoors.

Like sulphur, selenium exists in a numberof different varieties or " allotropic modi-fications," as they are termed.

Alpha -selenium (a -selenium) is the brick -

MOLTENSELENIUM

LID SEALEDWITH CLAY

meat, but is a mixture of various modifica-tions of selenium. It is, however, the formof the element which becomes light-sensitive on being subjected to careful heat -treatment.

Selenium combines readily with manymetals to form velenide.s, just as sulphurcombines with metals to form sulphides.Mix intimately equal quantities of powderedselenium and fine iron filings. Place themin a test-tube or at the bottom of an oldcan and heat the mixture strongly. Justbelow red -heat a glow will spread throughthe mass. After this appears, heat a littlemore strongly and then allow the mass tocool down. It will now consist of ironselenide, mixed with more or less un-changed iron filings.

A Further ExperimentNow comes an experiment which 'Pm

be performed out-of-doors owing to the badodour of the generated gas. Place in asmall flask fitted up with a delivery tubesome of the iron selenide prepared in theforegoing experiment and pour into the flaska small quantity (sufficient to cover theiron selenide) of dilute sulphuric or hydro-chloric acid. Have in readiness a vesselcontaining cold water and arrange mattersso that the delivery tube of the flask dipsbelow the water.

The action of the acid on the iron seleffidewill result in the liberation of hydrogenselenide (" selenuretted hydrogen "), H2Se,

RECEIVER FORSELENIUM DIOXIDE VAPOUR

SPIRITAo'LAMP

TIN CONTAINING MIXTURE OF POTASSIUM CHLORATEAND MANGANESE DIOXIDE

An experiment with selenium showing the apparatus required for making selenium dioxide.

red powder in which form selenium is pre-cipitated from its chemical solutions.Beta -selenium 0 -selenium) is the blackcrystalline powder which is obtained bypassing sulphur dioxide gas into a heatedsolution of selenious acid. Gamma -selenium (7 -selenium) is the dark -redcrystalline mass which is obtained by dis-solving selenium in carbon disulphide.Delta -selenium (s -selenium) is the lump orpowdered selenium of commerce. Veryprobably it is not a pure form of the ele-

a gas very similar to sulphuretted hydrogenin properties, but having, if possible, a stillmore unpleasant smell. It is for this reason,and also on account of the fact that someexperimenters find hydrogen selenide gassomewhat irritating to the eyes, that theexperiment should be carried out in anopen space.

Hydrogen selenide is soluble in water.Its solution in water, however, is not verystable. Quickly it will begin to decomposeand it will deposit brick -red selenium



(a -selenium) on the bottom and sides ofthe containing vessel.

Ammonium SelenideIf instead of leading the hydrogen

selenide gas into water, it is led intoa dilute solution of ammonia, anothercompound-ammonium selenide-will beformed. But ammonium selenide, also, isnot a very stable substance. Within a few

Making hydrogen selenide I-12.Se. Iron selenide anddiluted sulphuric or hydrochloric acid are placed in theflask, the hydrogen selenide evolved being bubbled

through water in the glass cylinder.

minutes a proportion of it decomposes andliberates selenium. This time, however,the liberated selenium is in the form ofa colloidal solution, which, as you will beaware, is not a true solution, but which inreality consists of a fine suspension ofselenium in the water. The suspendedparticles of selenium are so fine that theycannot be seen except through an ultra-microscope. Nevertheless, their presencegives a magnificent ruby colour to theliquid.

In this connection it is worth notingthat if a trace of selenium is added to moltenglass a similar colour is produced throughoutthe mass of glass. The principle is thesame, the selenium being spread throughoutthe glass in a colloidal form.

If instead of ammonia or water, as in theabove experiments, the hydrogen selenidegas is passed into a dilute solution ofcaustic soda, the resultant liquid will con-tain sodium selenide in solution. Like thewater and dilute ammonia solutions ofselenium, this solution also is unstable, andwill precipitate brick -red selenium.

If dilute sulphuric or hydrochloric acidis added to any of the above three solutions,pure selenium in its brick -red form will beprecipitated almost instantly. It can thenbe filtered off through a filter -paper, washedand dried for preservation or future ex-periments.

Before leaving the subject of hydrogenselenide, mention must be made of one veryuseful application which will be of interestto all amateur photographers. This is themaking of selenium -toned photographs,about which little is heard at the presentday.

In order to make these prints it is neces-sary to start with a black -and -white gaslightor bromide print. This should be immersed

in the following " bleaching solution " untilthe black and white image is " bleached "to a faint brown colour :-

Potassium ferricyanide . 100 gr.Potassium bromide . . 150 Water . oz.

or 11 gm.16

150 c.c.Rinse the bleached print in water and

then transfer it to the solution obtained bypassing hydrogen selenide gas into water,dilute ammonia or dilute caustic soda solu-tion. A chocolate -brown image will developupon the print immediately. The printshould not be immersed in the hydrogenselenide solution for more than one minute,otherwise the whites of the photographwill be discoloured. It should then bethoroughly well washed and dried. Itsimage will now consist of silver selenide.

Selenium DioxideSelenium dioxide, SeO2, is an interesting

selenium compound to prepare. It isanalogous to sulphur dioxide, SO2, butunlike the latter, which is a pungent gas,selenium dioxide is a white crystallinesubstance. In order to prepare thismaterial rig up the simple apparatus shownin the accompanying sketch. A mixture ofpotassium chlorate and manganese dioxideis heated in an old coffee or cocoa tin. Thisis better and cheaper than using a hard -glass test tube for the purpose. The lid ofthe tin and the area at which the delivery -tube passes through it should, of course, bewell luted with clay in order to provide anefficient seal to prevent the escape of thepure oxygen gas which will be generatedas a result of the heating. The oxygen gasfrom the chlorate mixture is led into a bulbtube, in the bulb of which a small quantityof selenium is gently melted. The exitfrom the bulb tube leads into a small conicalflask or other suitable vessel. When theoxygen comes in contact with the selenium,the latter will take fire and it will burngently with a peculiar lambent flame.White clouds of selenium dioxide, resultingfrom the combination of the oxygen withthe selenium will be evolved and these willcondense to long white crystals in theconical flask or other receptacle which actsas a " receiver." Some of these crystalsought to be collected and sealed up in aglass tube as permanent specimens.

To the remaining crystals a small quan-tity of hot water should be added. Asolution of selenious acid will now be formed,the selenium dioxide having combined withthe water in accordance with the followingequation :-

Se02 H50 = H2SeO3.Selenium Water. Seleniumdioxide. acid.

This reaction, you will observe, is similarto that in virtue of which sulphur dioxide,SO2, combines with water to form sul-phurous acid, H2S02. If oxides are dis-solved in this acid, selenites are obtained.Selenious acid, however, is not very stable.If zinc, magnesium, mineral acids or evena stream of sulphur dioxide gas is allowedto act upon the solution, selenium will beprecipitated.

Selenic acid, H5Se04, which, as will benoted, is the selenium equivalent of thewell-known sulphuric acid, H2SO4, is amuch more stable acid. It is a strong acidalso, and it carries the proud distinctionof being the only single acid known whichwill dissolve gold.

Selenic AcidTo make selenic acid, one has to go a

rather roundabout way. If silver nitrate

solution is added to a solution of seleniousacid, a precipitate of silver selenite, AgaSe03, will be obtained. If this salt iscollected and suspended in water (it isinsoluble in water) and a few drops ofbromine added, the following reaction willoccur :-Ag,Se0, 1150 Br2 = 2AgBr -I-H2Se04.

Silver Water. Bromine. Silver Seleniceelenite. bromide. acid.

The insoluble silver bromide may be filteredoff, leaving the aqueous solution of selenieacid to be concentrated by heat. Thismethod of preparation, however, is not avery satisfactory one on account of theexpense of silver nitrate.

A less expensive method of preparingselenic acid consists in fusing to red heat amixture of about equal quantities ofpowdered selenium and saltpetre (potassiumnitrate). A chemical reaction will proceed,resulting in the formation of potassiumselenate. The fused mass is dissolved inwater, and to the solution a solution of leadnitrate or acetate is added until all theselenium is precipitated as lead selenate.This insoluble compound is suspended inwater and a stream of sulphuretted hydrogengas is passed through the liquid. The leadis precipitated as lead sulphide, leavingthe free selenic acid in solution. It shouldthen be carefully concentrated by heat.

Selenic acid, like sulphuric acid, is avery strong acid. Metallic oxides, hydrox-ides and many metals themselves (includ-ing gold) dissolve in it to form salts knownas selenates. These are easily crystallisable,and may be prepared in this manner.

SelenidesWe now arrive at the large class of

selenium compounds known as selenides.These are usually readily prepared bypassing a stream of selenuretted hydrogengas into a solution of the metallic salt.For instance, if a stream of hydrogenselenide is passed into a solution of silvernitrate or lead nitrate, silver and leadselenides respectively will be precipitated.These are absolutely insoluble in water.

Pure selenium in its glassy condition. This is thematerial from which the light-sensitive form of the

element is prepared.

They may thus be filtered off, washed,dried and preserved in glass tubes. Whenacted upon by hydrochloric or sulphuricacids, selenides evolve pure hydrogenselenide gas. Herein, therefore, we have amethod of preparing selenuretted hydrogenin its pure state.

When any compound containing seleniumis fused by a hot flame on a block of char-coal, it invariably gives off a characteristichorse -radish odour. This constitutes adelicate test for the presence of selenium.

Selenium in its light-sensitive form isprepared by very carefully melting thelump variety of the element and then bycautiously allowing it to cool, therebyobtaining it in an annealed condition.Selenium, however, is given its light -sensitivity after being incorporated inelectrical cells. It cannot be made light-sensitive by purely chemical methods alone.

If selenium is gently melted in a bulbtube and a slow stream of chlorine gas(generated by the action of hydrochloricacid on manganese dioxide) passed over it,selenium dichloride, Se3C1 will be formed.



The New PelmanismSIR HERBERT BARKER'S

GREAT TRIBUTE

" Take this Course-all of you," he says.4. D USINESS is improving ; international

I-Jrelationships are becoming more reason-able and cordial ; the whole world is stirredand awakening to the clamant necessity ofputting its mighty house in order.

" Eager hearts and ambitious minds areasking what they can do to help this greatwork for humanity-The answer is : Makeyourselves more efficient-in body, mindand character.

" Can we do this'? I say most emphatically,We can, and by that simple, alluringlypleasant, and marvellous system which thedenizens of the entire earth know asPelmanism. No one who has investigatedits methods can doubt this, and the im-posing and impressive testimony of manyof our greatest men constitutes, I shouldsay, a unique record of praise.

" I always thought it quite impossible thatthe old Little Grey Books ' could be im-proved upon, but the new ones have-if Imay say so-achieved the impossible, andmade the perfect more perfect.

" Take this Course-all of you-and lifewill have a new beginning whatever yourage. You will, each day, more and moredeeply realise the quiet but intense joy andsatisfaction of knowing with certainty thatyour mind and character are steadily beingbuilt up, stone by stone ; that your brainis being fortified and clarified ; your willstrengthened, and life becoming what it wassurely intended to be, a glorious privilege-s blessing beyond all price.

" Mr. W. J. Ennever has indeed bestowedan inestimable boon upon mankind andrichly deserves all that is best of his fellow-men. His name will be honoured in thehistory of progress, as it is respected to -dayby the thousands of men and women whoowe him a great, unpayable debt of grati-tude. Never has the world needed Pel-manism more than to -day."

(Signed)

14,A Course for the Modern Mind

Pelmanism has taken another step for-ward. The rapid advances which have beenmade in Psychological knowledge and thenew intense demands which modern life ismaking upon each one of us, have calledfor a corresponding advance in Pelmanism.For many months, under the personaldirection of Mr. Ennever, and with the co-operation of eminent psychologists andbusiness authorities, the great work ofrevising and expanding the Course has been

carried on. New sections dealing with suchimportant subjects as " The InferiorityComplex," " The Money -Brain " and" Business Judgment " have been added.The " 12 Little Grey Books " have beenincreased to 15, and the New Pelmanismwhich was first introduced to the public onNew Year's Day, 1935, is undoubtedly thefinest and most complete system of trainingthe mind and the senses and developingPersonality the world has ever seen.

Increases Earning -Power

It enables those who follow it to masterthe art of Self -realisation and Self-expres-sion. It shows them how to conquer anymental defects which may be troublingthem and how to develop such usefulqualities as Observation, Concentration,Initiative, Self-confidence, Self-reliance,Will -power, Organising Ability and CreativeImagination. It shows them how they canincrease their all-round efficiency andearning -power and thus improve theirpositions in life. It is in fact a modernCourse for the modern mind, and everyreader who wishes to train his or her mentalfaculties to the highest efficiency by themost up-to-date scientific methods shouldwrite for full free particulars to -day.

" Develops Maximum Efficiency "

" Truth's " report on the New PelmanCourse is a most enthusiastic one.

" Pelmanism," it says, " develops themaximum efficiency in any given mentalmachine by a process comparable to theway in which physical training develops thehealth, strength and agility of the body.It enables the student to understand thenature of mind and its intricate processes ;it analyses and discusses such mental defectsas he may suffer from-lack of Concentra-tion, bad Memory or Feeble Will-Power-and shows how these may be remedied ; itgives point, direction and discipline to hislife generally, and sets him working con-fidently towards the fulfilment of hisultimate aim and the enjoyment of a fullerlife. In short, it teaches him scientificallyhow to succeed.

" A well -trained mind," it continues, " isnot necessarily an expensively educatedmind. Any person with merely an ele-mentary education can train his or hermind by the Pelman System into athoroughly efficient instrument, splendidlyequipped in the technique of living."

It follows from this that no one whowishes to succeed in life, to earn moremoney, to rise to a higher and more respon-sible position and to enjoy a fuller andricher existence can afford not to take theNew Pelman Course or to miss the oppor-tunity given to readers tu-day to enrol onthe most convenient terms.

Full Report and Descriptive Book FreeTo -day

If therefore you are troubled with Inde-cision, Mind -Wandering, Procrastination,Timidity, Shyness, Forgetfulness, LostNerve, Morbid Thoughts and Fears, De-pression, Want of Confidence, or False Feel-ings of Inferiority, or if you wish todevelop :-

-Concentration-Judgment-Self -Control-Imagination-Initiative-Observation

-Foresight-Tenacity-Self -Confidence-Strength of Will-Self -Expression-Organising Power

-Resourcefulness -Decision-Courage -Creative Imagination-Perseverance -Driving Force-Optimism -A Good Memory

and a forceful, reliable Personality, youshould write for particulars of the NewPelman Course to -day.

The Coupon is printed below. Fill it upand post it to -day to the Pelman Institute,130 Pelman House, Bloomsbury Street,London, W.C.1, and by return of post youwill receive, free of cost and without in-curring the slightest obligation :

1. A copy of an illustrated book entitled" The Science of Success," which tells youall about the New Pelman Course and showsyou how you can enrol on the most con-venient terms.

2. A reprint of the special report issued by" Truth " on the New Pelmanism whichcontains a most interesting description ofthe finest and most complete method oftraining your mind on scientific lines andincreasing your Earning -Power and Effi-ciency the world has ever seen.

Write (or call) to -day, and the above willreach you by return, gratis and post-free.

FREE COUPON

To the Pelman Institute,130 Pelman House, Bloomsbury Street,

London, W.C.1.Please send me, gratis and post free :1. A copy of " The Science of Suc-

cess," with particulars showing howI can enrol for a Course of Pel-manism on the most convenientterms.

2. A reprint of " Truth's " specialreport on the new enlarged Pel-man Course.

NAME

ADDRESS

OccupationAll correspondence is confidential.

PELMAN (OVERSEAS) INSTITUTES: PARIS:80 Boulevard Hausmann. NEW YORE: 271 NorthAvenue, New Rochelle. MELBOURNE: 396 FlindersLane. D RBA -V : Natal Bank Chambers.CALCUTTA: 102 Clive Street. DELHI: 10 AliporsRoad. AMSTERDAM: Damrak, 68. JAVA:Eromhoutweg 8, Bandoeng.


316 NEWN ES PRACTICAL MECHANICS April, 1935

How many MILEShave I walked?

The PEDOMETERwill tell you if you carry onein your pocket-it recordsI miles up to 100 miles andcan be set to zero at any time.

1816 Post free.Catalogue P255 sent on application.

W. F. STANLEY & Co. Ltd' LONDON-.G.1286 HIGH HOLWBORN

DRAWING INSTRUMENTS AND ALL MATERIALS.

The "UNICORN" Electric Drill1" CAPACITY. BRITISH MADE

Efficient, a model ofaccuracy andworkmanship, andtrouble -free qualitiesare the features ofthis drill. Its equipment comprisesa powerful A.G. or D.C. Motor,voltages 100/120, 200/230, 230/250,with Armature Shaft in ground alloy steel. Hobbed gears inmetal housing. Hoffman ball thrust. Keyless chuck, }-in.capacity. Aluminium die cast handle. Current consumption175 watts, using }-in. drill on mild steel. 8 ft. Cab tyre flexwith earth wire. Weight 5 lbs.

PRICE £2 . I5 . 0Carriage Paid. Please state voltage.

Send for Illustrated leaflet to:- Tele. : GULLIVER 3739.

CORONA ENGINEERING CO., Leighton Place, Kentish N.W.5

ECONOMIC ELECTRIC CO.TWICKENHAM, LONDON, S.W.

16/6, post 6d.

Home Broadcasting. With thissuper instrument you can obtainwonderful results by simply con-necting to pickup terminals of yourreceiver. Complete, as illustrated,with transformer and volume con-trol and instructions.

Price 16/6, post 6d.ECONOMIC BOAT MOTORS.

For 4 ft. Launch, 15/-; 5 ft. Launch, 17/6.Dry Battery type. 4 -volt. Consumption

'3 amp. 9/- and 13/6. Post 6d.Shocking Coils, 2/6, 3/6, 5/6, 9/6. Post 4d.Large Cabinet Pattern, complete with 2 drycells and lull set 01 electrodes, 32/6. Post If-.Send for our 72 pp. List, 1,000 itemsfor instruction, amusement and work-shop, 3d., post free.

THE LAST OF THESPECIAL OFFER OFMICROSCOPES!

as illustrated.Each model has inclinable body, swingmirror, stage clips, and is nicely finishedin Black Crystalline

Enamel and brightNickel Plating.SHARP DEFINITIONIS OBTAIN-ABLE and GOOD WORK CAN BE

Model C. Height 5i in., sliding focus, magnification 25x linear. Price 5/ -Mode. D. Height 7 in., sliding focus, circular stage magnifLation 9/6

50 x linear ... . . .. PriceModel E. Height 7 in., rack and pinion focusing, magnification 12/650 x linear, square stage ...

Price 1 -

Post free Gt. Britain.Lists of Telescope

Microscopes, Binoculars,Lanterns etc.BROADHURST CLARKSON & CO. TELESCOPE63 FARRINGDON

ROAD, LONDON, E.C.IHOUSE

STRANDMAGAZINE

I"Big April Number

CONTRIBUTORS INCLUDE-

P. G. WODEHOUSEDENIS MACKAIL

THOMAS BURKEJOHN HASTINGS TURNER

E. PHILLIPS OPPEN HEIMSAPPER "

F. BRITTEN AUSTINMARGERY SHARP

E. V. LUCAS, etc.

Now on sale at all newsagentsand bookstalls

Geo N ewnes Ltd.

RECTIFIERSFor the operation of Model Electric Railways, etc.

MODEL 103M. Output 6, 8 or 10 volts at 3 amps.

£2 2 0Incorporating Westinghouse Metal Rectifications

COMPLETE LIST ON REQUEST

VARIABLE RESISTANCES, REVERSING RESISTANCECONTROLLERS, ELECTRO-MAGNETIC RAILWAY POINT

OPERATING MECHANISM, etc., from

SHENPHONE ELECTRICAL PRODUCTS226 HIGH RD., LEYTON, E.10

OWIRELESCEVISION

Television is the comingboom in wireless-it willbring even greater pros-perity to the industry andcreate many more opportunities for acareer. Men who foresaw the broadcast-ing boom made good-be trained andprepar d for this television boom which

At the WIRELESSCOLLEGE studentsreceive training in all thelatest developments in all

branches of the Wireless profession.Marine, Aircraft, Manufacturing, Design-ing, Experimenting, Sales and Service, etc.College on sea front. Wrgte dor free

must follow as surely as night follows day. pro'fertcs.STUDENTS ACCEPTED AS BOARDERS. TRAININGFEE CAN BE PAID AFTER APPOINTMENT SECURED

The WIRELESS COLLEGECOLWYN BAY

N. WALES



A 4016V 1 1 1 1

EVE IMENTERTHE series of receivers formerly

described in these pages have, withoutexceptiOn, dealt with receivers having

three or more valves. The simple two-valver did not seem to call for space, sincemost readers are able to wire up a simpledetector stage with one low -frequencyamplifying stage. One is always, however,apt to lose sight of the fact that a newgeneration of wireless enthusiasts springsup every few months, as is proved by themany requests we receive for designs ofcrystal sets, one -valve sets and two-valvers,hence, this month we have designed aspecial two-valver, employing a well-knownsatisfactory circuit and modern components.We had in mind when pre-paring this design a receiverwhich could be used as a use-ful introduction to a moreambitious receiving set. Afteradjusting it, however, itdeveloped into a fascinatingpiece of apparatus which inmany respects is equivalent tosome three-valvers.

Modern AppearanceTo give it a modern appear-

ance we have employed awooden metallised chassiswhich gives the visible portionof the receiver a clean appear-ance and enables componentsnot in need of adjustment tobe conveniently tucked awayunderneath.

The receiver is certainlycheap, and it may be made ina couple of hours. Notwith-standing the economy of com-ponents and the few wiresemployed, it is a top-notcher from thepoint of view of quality and number ofstations received. A modern screened coilis used which under test revealed itself tobe entirely efficient, with no trace of break-through or restricted tuning range.

Careful adjustment of the pre-set con -

lit. 911

THE MONARCHTWO-VALVER

A three-quarter front view of the receiver,showing the neat layout of the components.

denser will improve selectivity and sharpenup the tuning.

The ConstructionThe first part to secure is the tuning coil,

which is attached to the baseboard by meansof two screws, then the variable condenser,

(Left) A rearview of theMonarch Two -valve receiver,and (Right) Anunderneath viewshowing thesimplified wir-ing and positionof components.

which is fastened from the underside of thechassis by means of screws which pass intoprojecting sockets at the base of the con-denser.

Next, drill 1 -in. holes for the valve -holders, and fix these by means of fourscrews, noting the relative positions of thegrids, that is to say, the grid of the detectorvalve is nearest the coil, whereas the grid ofthe pentode valve is nearest the right-hand side of the chassis. In other words,the two plate legs face one another. Next,screw down the pre-set condenser and thegrid -bias battery clips.

The two brackets which carry the on -offswitches and the wave -change switch should

next be secured, as well as thesmall earthing tag to the leftof the on -off switch. Nowinvert the chassis and securein the exact centre of the frontedge the bracket which carriesthe reaction condenser. Nowscrew the binocular choke, the.L.F. transformer and the 2-mfd. fixed condenser to thechassis, and, finally, drillthrough the back of the chassisfor the speaker and aerial andearth clip.

Wiring the ReceiverThe Monarch Two-valver is

now ready for wiring, whichshould be carried out in thefollowing order :-

Connect the left-hand ter-minal of the wave -changeswitch to terminal 5 on thecoil base (the coil should bemounted with terminals 5and 2 at 9 o'clock and 3

o'clock, respectively) ; connect terminal 6of the coil to the left-hand terminal ofthe pre-set condenser, solder a wire to theleft-hand tag of the variable condenser toterminal 1 of the coil base, continuingthis wire through a hole drilled in the base-board to a .0002-mfd. tubular condenser,



the other end of which is secured to thegrid terminal of the detector valve. Alsofrom this grid terminal connect one end ofthe 2-megohm grid -leak, and the other endof the grid -leak to the filament terminalnearest to the transformer. Turn the setthe correct way up again and connect awire from the left-hand terminal of theon -off switch to the nearest terminal on thefuse. The other side of the on -off switchis wired vid a hole in the baseboard to thefilament terminal nearest the 2-mfd. fixedcondenser, this same wire continuing to thefilament leg to which the grid -leak isattached.

The Earthing ConnectionNow solder a wire to the earthing tab

secured to the baseboard slightly to theleft of the on -off switch and pass this wirethrough a hole in the baseboard to thefront terminal of the 2-mfd. fixed condenser,to which it is soldered. Now wire up thetwo other filament legs ; bare this wiremid -way and solder a wire to it, the otherend being connected also to the frontterminal of the 2-mfd. fixed condenser.The back terminal of the 2-mfd. condenseris wired to the H.T. positive terminal of thelow -frequency transformer, this same wirebeing continued and connected to one sideof the 25,000 -ohm fixed resistance, theother side of the latter being connected toloudspeaker positive terminal of the speakerstrip. This same terminal is also connectedto the centre pin of the pentode valve -holder.

(Continued on page 320.)

LIST OF COMPONENTS FOR THEMONARCH TWO-VALVER

One Metaplex Chassis, 10 x 8 in., with3 -in. runners (Peto-Scott).

One Type GOB Tuning Coil (Ward &Goldstone).

Two Chassis -mounting Valveholders ; one4 -pin and one 5 -pin (Clix).

One 0005-mfd. Tuning Condenser withDrive (J.B. " Nugang").

One -0003 - mfd. Reaction Condenser(Polar).

One 5 :1 L.F. Transformer (B.R.G.).Three Tubular Fixed Condensers ; two

-0002 mfd. and one 1 mfd. (T.M.C.).Three 1 -watt Resistances; 2 megohms.

20,000 ohms and 50,000 ohms (Dubilier).One 2-mfd. Fixed Condenser (T.M.C.,

Type 25).One H.F. Choke ( Ward & Goldstone,

Binocular).Two Push -Pull Switches (Bulgin

" Junior ").One 100-m.a. Fuse and Holder (Micro -

fuse)One .0003-mfd. Pre-set Condenser (Ward

& Goldstone).Two Terminal Socket Strips ; one A and

E, and one L.S. (Clix).One G.B. Battery Clip (Bulgin No. 1);Four Wander Plugs ; marked H.T. +,

H.T. -, O.B. + and G.B. - (Clix).Two Spade Terminals ; L.T. + and

L.T. - (Clix).Connecting Wire, Flex, etc.Two Valves ; one V .P. 210 and one

Y.220 (Hivac).One Amplion Dragon Loudspeaker.

TOP- AND SUB -CHASSIS WIRING DIAGRAMSOF THE MONARCH TWO-VALVER

GB.84rreRYCZ/PS

GB -

4./.4vecliANGE5, .5'sv/rrN

o005 MED C172nwriG CavoErvsER

68+

A18

AER/AiCO/L.

E

A/

112

2MroC7

2

47,1

20000OHMS

0002 MCo

/CS//1410

"Pt

-Ca 000avms '0002/O

0003 ,*D,PE.scrion,CoNo. C2

Z. 7-

Nr-

G

A SPLENDID HANDBOOK! 1

"50 Tested Wireless Circuits." By F. J. Camm.2/6, or 2/10 by post, from Geo. Newnes Ltd., 8-11 Southampton

Street, Strand, W.C.2.



THE CHOICE OF ALOUDSPEAKER

We most of us know just what we would like,but unfortunately, many of us have to choosethat which is nearest to our ideal and is notbeyond our purchasing power.It is for this reason that in this month'sadvertisement we are listing the completerange of " Amplion " Permanent MagnetMoving Coil Speakers.Each model is unquestionably wonderful valuefor money and we stake our reputation uponyour being fully satisfied with your choice.FIRST we call your attention to the latestAmplion-the " Dragon " model which Mr.F. J. Camm (the Editor of "Practical Mechanics")has specified for his " MONARCH " TwoValver described in this issue.

HERE IS THE"DRAGON"

PRICE

29/6ONLY

See the ,6 good words "used by Mr. Cammwhen writing aboutthis on page 272 of theMarch issue.

THE " DRAGON "

HERE ARE THE OTHER AMPLION " MODELSModel MC 22 - - (7 -inch cone) 32/6

The " Audiola " (9 -inch cone) 42/6The " Lion" -

" Lion " Super -All fitted with Universal Transformers.

AMPLION CABINET SPEAKERSMC 33 I 3" x 13" x 51"MC 44 151" x I 31" x 6r"LION " - (7' cone) I x 1514" x 6r

All cabinets are of highly polished selected Walnut.

Descriptive Leaflets dealing with each modelare obtainable. Just send a Post Card

stating which models interest you.

(7 -inch cone) 47/6

(10 -inch cone) 55/-

47/663/-75/ -

AM PL ON ( 932) LTD82-84 Rosoman St., Rosebery Avenue, London, E.C.I

Telephone : Clerkenwell 5440.6441.

HIVAC CONSISTENTLY SPECIFIED

MR. F. J. CAMM

Specifies

HIVACfor the

" MONARCH "TWO VALVER

denotes the valvesrequired

For greater out-put and im-proved qualitychoose one ofthe Hivac powervalves and try itin your presentset. You trill bepleased.

British made by :-

2 -VOLT BATTERY VALVES ... FROM 3/9HIVAC

H 210 H.F. Amplifier... ... ... 3/9D 210 Non-Microphonic Detector ... 3/9DDT 220 Duo -Diode -Triode 7/-L 210 L.F. Amplifier ... 3/9P 220 Small Power ... 5/8PP 220 Medium Power 8/6PX 230 Super Power ... 7/6Y 220* Medium Power Output Pen.

Z 220 Super Power Output Pen. TypeB 230 Class " B "DB 240 Driver Class " B "QP 240 Double Pen. Type for Q.P.P....SG 216 Screen Grid ... 10/6S El 220 High Slope Screen Grid... ... 10/6VS 215* Variable -Mu Screen Grid ... 10/8HP 215 H.F. Pentode Type ... 10/8VP 215 Variable -Mu H.F. Pen. Type 10/64.VOLT MAINS VALVES (A.C.) ... FROM 9/6AC/HL Detector 8/6AC/DDT Duo -Diode -Triode 12/6

Small Power ... 12/6Output Pentode Type ... 15/6High Slope Output Pen. Type 15/6Screen Grid Amplifier... ... 134High Gain S.G. Amplifier ... 13/6Variable -Mu Screen Grid ... 13/6Variable -Mu High Gain S.G.... 13/8H.F. Pentode Type ... 13/6

AC/VP Variable -Mu H.F. Pen. Type 13/6U U120/350 Full Wave Rectifier (I.H.C.) ... 10/6U U120/500 Full Wave Rectifier (I.H.C.) 15/-

AC/YAC/ZAC/SLAC/SHAC/VSACIVHAC/HP

10/610/810/615/619/6

141YACHIGH VACUUM VALVE THE SCIENTIIFIC

CO. LTD.,113-117 Farringdon Rd.,London, E.C.I BRITISH --*7 MADE

VALVE

IMPROVE QUALITY AND RANGE

661Every one of these Clix perfect contact com-ponents (as specified by the designer) is essen-

tial to perfect results from theMONARCH TWO-VALVER

Chassis MountingSTRIPS

2 Socket Strips withTerminals A., E., or L.S.

6d. each.

/ GP /7 *, * /Put your name on our mailinglist "P.M." for all literature.

Chassis MountingVAL VEHOLDERS4 -pin 8d. 5 -pin 9d.

Spade TerminalsL.T.+ L.T.- lid; ea.

Master PlugsFor H.T. andG.B. Engraved.

id. each.

LECTRO LINX LTD79a Rochester Row, London, S.W.I


320 NEWNES PRACTICAL MECHANICS April, 1935(Continued from page 318.)

The panel layout of the Monarch Two -valuer.

Completing the ReceiverThe loudspeaker negative socket is con-

nected to the plate socket of the 5 -pinvalveholder. The low -frequency trans-former, by the way, should be connectedwith the plate and grid -bias terminalsnearest the reaction condenser. The plateterminal of the L.F. transformer is con-nected to the front terminal of the binocularchoke and the grid -bias terminal of thetransformer, the grid -bias battery leadbeing taken direct to the grid -bias terminal.The grid terminal of the transformer isconnected to the grid of the pentode valve -holder. The 1-mfd. tubular condenser iswired between the plate socket of thedetector valveholder and the earth terminal.A 50,000 -ohm fixed resistance is connectedto the plate socket of the detector valve -holder, the other end of the resistance beingconnected to one of the leads of the batterycords, as later described. Now connect awire from terminal 4 of the tuning coilthrough a hole in the baseboard to thenearest terminal on the reaction condenser,and connect a wire from the other terminalof the reaction condenser to the rearmostterminal of the binocular choke. Continuethis wire in the form of a flexible leadthrough a hole in the baseboard to forma connection for the top terminal of thescreen -grid valve. A tubular condenserof .0002 mfd. capacity is also wired be -

tween the re-action condenserand the frontsoldering tag ofthe 2-mfd. fixedcondenser. Theright-hand ter-minal of thewave - changeswitch is con-nected by meansof a wire passingthrough a hole inthe baseboard tothe nearest fila-ment socket ofthe 5 -pin valve -holder.

It only remainsto connect thebattery cords tothe various posi-tions indicated inthe wiring dia-gram on p. 318.Notice that theL.T. - lead goes

to the filament valve -socket of the detectorvalve holder, the L.T.+ terminal passesthrough hole 2, and to the on -off switch,H.T. - passing through the same hole andbeing connected to one side of the fuse.

H.T.+ 1 is secured to the free end of the50,000 -ohm fixed resistance R1, and inorder to relieve this of any strain it issuggested that the bunched battery cordleads should be firmly attached to a con-venient part of the chassis by means of aleather strap fastened down by means oftwo screws.

The H.T.+ 2 lead goes to the fifth pinof the pentode valveholder. Notice thatthe G.B.- lead passes through hole 4 andis taken direct to the G.B. terminal of theL.F. transformer, whilst G.B.d- is con-nected to the metallised baseboard via thescrew securing the pre-set condenser. Itsbared ends must, of course, make goodcontact with the metallised baseboard.

A 2 -volt accumulator will be required, a120 -volt H.T. battery, a 9 -volt grid biasbattery, and the Amplion Dragon loud-speaker. Suitable plugs for the terminalstrips will also be needed.

C>A'FcO-

1=

VI

N.T.

0000/-0000UNGB. /

TRANS.

G.B.

Df

LS.

OH.T.

OH.T,-t2

t>":0-0z. r1'

The circuit diagram of the Monarch Two -valuer.

Vacuum Cleaning a Ship's Oil TanksOIL sludge gradually collects in aship's fuel tanks, which has to becleaned out from time to time. This

used to be done by blowing out with steaminto the sea. When the Board of Tradestopped this objectionable practice, cleaningout by hand with bucket and shovel wasresorted to. This messy proceeding hasnow been superseded by a vacuum -cleaningservice at all the larger ports. When a shipwants to clean tanks, a service barge comesalongside, which is fitted with pumps, hoseand receiver tanks. The 6 -inch armouredhose is lowered into the hold perhaps 70 ft.down into the oil tanks in the doublebottom. Any inflammable gas is firstsucked off so that men can work in thetanks without respirators and then thesludge is softened with steam. Vacuum isturned on and the pumps start to suck upthe sludge. As the pumps could not raisethe sludge 70 ft. in a single lift, air is

ITEMS OF INTEREST

admitted along with the sludge so that itascends as a fine spray. So powerful is theair draught that solid bodies, such as straybolts and rivet heads are sometimes foundin the receiver tanks.

Gases from the AirIN the air around us exist decimal per-

centages of the rarest of the chemical ele-ments-the inert gases argon, krypton,

xenon, neon and helium. In 1900 theywere chemical curiosities. To -day they areused in millions of cubic feet for filling gas -filled electric light bulbs. To meet thisdemand, air is liquefied and fractionallydistilled at temperatures 200° C. belowfreezing point. From 1,200 tons of aironly 1 lb. of xenon is obtained and 70 lb.of krypton, although the quantities of

neon and argon are 250 lb. and 11 tonsrespectively.

Electric light bulbs were originallyvacuum filled." But the vacuum allowed

white-hot metal to evaporate off the fila-ment which deposited on the glass andgave a dark film. To stop this the bulbswere filled with nitrogen. Nitrogen slowlyattacked the filament, so argon, which isinert, was substituted. It is estimated thatthe use of argon has reduced the nation'selectric light bulb by 20 per cent. If thegases xenon and krypton were substitutedfor argon another 25 per cent. could beknocked off, as they would insulate thefilament from heat losses more effectivelythan argon. But the cost of working upthe traces of these two gases from air wouldmake the saving too expensive for the manu-facturer. Besides it is probable that thefilament type of lamp will be replaced bymetallic vapour discharge lamps in the nearfuture.



NOW that some of the Southern Rail-way Company's main lines, and manyother suburban and metropolitan

lines, are being completely electrified, agreater amount of interest seems to begrowing in the minds of model railwayenthusiasts. Although the majority do notgo so far as to instal motor -driven coachesin place of locomotives with steam outlines,they are very much intrigued by suchfeatures as traffic type light signals in placeof semaphores, and the automaticcontrol of electrically propelledtrains as they enter andleave the block sec -

tracks. .................

IEIL___001,4=;=rmi-I .1,v, ..................vli

Com

Fig. 2.-A scaledrawing of the

relays.

:A1(111.70.3(10E

C),(S)0tu

-E-0e--

'Re

tions of the

........................

.....

&mom

Inches / 31.,.1.1.1...,.1.1

on a big railway, should a signal lamp fail,that is to say burn out, the section of trackwhich it controls is rendered dead, and atrain in that section is stopped. Thisresult is attained by means of a delicatethermostat attached to the lamp, thethermostat controlling a relay.

Fortunately, automatic control canbe very much simplified formodel working, and the .........

.......is one which in-volves the

.................

system described here

least amount ofapparatus and wiring,

and consequently avoidscomplication.

..........

No RailwayAccidents

There is a fascinationin knowing that if one has two

or three trains running on thesame line on a circular railway, eventhough they do not all run at the samespeed, one train can never overtake another,and that head- and rear -end collisions cannever occur, because the fast train is auto-matically pulled up in the block sectionbehind that occupied by the slower train,whilst the signal lights of the " dead "section go to danger.

It may be thought that the system orscheme must be a very elaborate one whichcan bring about such results, and in actualfull-size practice it is rather complicated,but this is because a great number ofrefinements are called for which are notnecessary in a model railway. For instance,

00

SECTION 2

00

SFerion 3

AN AUTOMATIC CONTROLAND SIGNALLING SYSTEM

By E. W. TWINING

Control Independent of SignalsAt first sight it may seem that as there

can be no driver on the train, the systemmust of necessity be more, rather than less,intricate, but this is not the case. This ispartly due to the fact that the control isindependent of the signals. That is to say,the signals, instead of controlling the track,are themselves worked from the trackrelays, and so it would make no differenceto the moving and stopping of the trains ifthere were no signals at all. Since there areno drivers on the trains to look at them,they are fitted for effect and not for use.

Actually, the intentional stopping oftrains at stations, and the restarting ofthem is at the will of the operator of the

DIReCTION OF

secnome*---

C's' RAIL

.3. RAIL L n If ii ii I

IV RAIL

IMOILBMI

1-11111111111-1 CONTROL PA' -`_L.

SWITCH.

Fig. I.-A wiring diagram. showing a length of line covering six block section.

MAMA

railway, who controls them from a switch-board as he also does the points to branchand main lines, which points are set andlocked electrically.

First, Second and Third RailsThe scheme is comparatively simple, and

the simplicity is dependent upon the out-standing fact that not only the conductorrail, from which the motor on the locomotivepicks up its current, but one of the runningrails as well is divided up into blocksections, and this running rail must beinsulated from the corresponding rail in thesections ahead of and behind it. The otherrunning rail is continuous and must bebonded together at all joints, so that itcarries the main current. Besides the rails,there is an insulated feeder wire laidparallel with the track.

For convenience the threerails are referred to as ......follows :-First rail : 0*.the continuous ......running

...... rail. Secondrail : the sectioned

.. . ..... or interrupted runningrail. Third rail: the con-

........ ductor of strip metal which is.......... usually placed in the centre of the

track and upon which the collector shoe,or brush, rubs.

It is not proposed to make any suggestionsregarding layout for a complete railway,because so much has been most ably done

writers in this direction as well asby manufacturing firms. The system sug-gested is applicable to any layout of eithersingle or double track with or withoutbranches, and all the needs of the permanentway and electrical departments are filled bygiving two wiring diagrams only, one show-ing a single length of line, which in the caseof double track can be considered as eitherthe up line or the down line, and a completeset of points with crossover for double track.

Diagram of CircuitsFig. 1 is a diagram showing a length of

line covering six block sections, the lengthof each section being made just as short oras long as may be found convenient for therailway, and for the frequency of the trainservice. In full-size practice the lengthsvary considerably, some of them extendingfor several miles. In a model they mayalso differ somewhat ; the short sectionsbeing made not less than, say, one and ahalf times the length of a train. Eachsection is protected and controlled by arelay provided with three contacts, whilst aconnection from the feeder wire is taken to

(Continued on page 323.)

00

SECTION51 ATION

5E010117

CLA7C,,,;+.



APRIL -the TIMEfor MODEL BOATINGOUT ON THE LAKE in the keen fresh breeze, with the sun shiningabove ! Let us watch the boat -dotted lake . . . white sails filling. . . motors buzzing . . . paint work glistening !There's a winner! That motor boat speeding past us-blue with awhite line and deck work. Her name 1 I just saw it. IOLANTHE.Here's a game little white and green boat. RALEIGH's the name ! Thankyou, sonny. I can see you're proud of her. Only a guinea? She's worth it!There's speed and grace personified-a " class " cabin cruiser or I'ma Dutchman ! MARGARET ROSE I An ideal name.That little yacht's a swift sailer-heading straight for the bank-we'll turn her-ah-the CYGNET!WHAT'S THAT 1 Someone's brought a " racer " out ! Why, she'sacross the pond in a twinkling-and course dead straight. What, sonnyShe's a "celebrity " here. That long, white speedboat ? BASSETT-LOWKE'S "STREAMLINIA." That's the sort of boat for me! =6,

IOLANTHE! IOLANTHE. 27k". Clockwork and electric 35/-.RALEIGH. 28". Clockwork. 21/-.MARGARET ROSE. 28". Clockwork andelectric 78/6.CYGNET. 20". 42/-.STREAMLINIA. 9 gns. complete. Sets ofparts for I gn. per month. Start building her!All described in 5.12 the new BASSETT-LOWKE SHIPS

CATALOGUE, price 6d. post free.See our stand at the Model Railway Exhibition, Central Hall, Westminster. April 23rd -27th.

BASSETT- LOW K E LTD. NOLONDON : 112 High Holborn, W.C. I. MANCHESTER : 28 Corporation St.

WHICH OF THESE IS YOUR PET SUBJECT ?CIVIL ENGINEERING GROUP

Specifications. Structural Design.Road Engineering. Structural Engineering.Hydraulics. Reinforced Concrete.Municipal Engineering. Sanitary Engineering.General Civil Engineering. Geology.

SURVEYING GROUPValuations. Surveying and Levelling.Heating and Ventilating. Building Construction.Clerk of Works.

COMMERCIAL ENGINEERING GROUPSalesmanship. Commercial Engineering.Advertising. Cost Accounts.Languages.

MECHANIC AL ENGINEERING GROUPWorks Management. Heat Engines.Press Tool Work. Workshop Practice.Maintenance Engineering. Fitting and Erecting.Metallurgy.Sheet Metal Work.Welding.Diesel Engines.Refrigeration.

Inspection.Ironfounding.Pattern Making.Draughtsmanship.

WIRELESS GROUPGeneral Wireless. Talking -PictureAdvanced Wireless. Engineering.Television. Radio Servicing.

AUTOMOBILEGarage Management.Electrical Equipment.

ELECTRICAL ETraction.Electrical Supply.Electrical Meters.Electrical Design.Installations.Electrical Engineering.

AERONAUTICALAerial Navigation.Aeroplane Design.

ENGINEERING GROUPClaims Assessing.High-speed Diesels.

NGINEERING GROUPMains Engineering.Telegraphy.Telephony.Alternating Currents.Neon Lighting.Power House Design.

ENGINEERING GROUPAero Engines.

One of these examinations would multiply your earning power ! WHICH ONE?A.M.I.C.E. A.M.I.W.T. G.P.O. Supt. of Traffic. Inst. Mun. Sc Cy. E. City & Guilds. London Matriculation.A.M.I.Struct.E.Sanitary Inspectors.A.M.I.H. & V.E.

A.Rad.A.M.I.M.T.

Patent Office Examiner.Handicrafts Instructor.

M.R.San.l.F.S.I.A.R.I.B.A.

A.M.I.Fire.E.A.M.I.E.E.

G.P.O. Prob. Inspector.Air Navigators'

Certificate.A.M.I.Mech.E. A.F.R.Ae.S. Inspector of Factories. A.M.I.A.E. Ground Engineers'A.M.I.P.E. B.Sc. Degree. Aircraft Apprentices. F.A.I. A.M.I.Ae.E. Certificate.

May we send you full particulars of our unique tutorial organisation ? Whatever your requirements,whether you desire a complete course of instruction, or tuition in some specialised subject, our Organisationis so planned that it will dovetail into your needs exactly.

As an indication of the strength of the B.I.E.T. Tutorial Organisation, it should be clearly noted thatwe alone guarantee to return full fees to any student who does not pass his chosen Examinationsuccessfully. In short, " If you do not pass, you do not pay."

Send to -day for a free copy of " ENGINEERING OPPORTUNITIES." This valuable 268 -page Guideshows clearly and definitely the way in which you may carve out a successful career in your chosen branchof Engineering, irrespective of your age, education or experience. Among a host of other things, it givesdetails of all the above -mentioned Courses and shows the easiest way to prepare (in the privacy of your ownhome) for any of the recognised Examinations we have listed.

" ENGINEERING OPPORTUNITIES " should most certainly be in your hands. Send for yourcopy at once-free of cost or obligation.

BRITISH INSTITUTE of ENGINEERING TECHNOLOGY410 SHAKESPEARE HOUSE, 29-31 OXFORD STREET, LONDON, W.1.

Austldwion Enquiries Box 3597S. Sorbet,. South African Enquiries : P.O. Box 4701. Jo'burg. Canadian Enquiries : 219 Bay Street. Toronto.



MODEL ELECTRIC RAILWAYS(Continued from page 321)

the movable armature of the relay. At theentrance to each section a signal lampstandard is placed having a red and a greenlight.

As will be seen from the diagram, thecurrent supply (the sketch shows a 12 -voltbattery) is taken to the feeder wire and tothe first rail. The circuit, when a motorof a train is on the track in, say, section 5,as shown in the diagram, is from the batteryto the first rail, from the first rail throughthe frame of the engine to the brushes andarmature windings of the motor, throughthe third rail, the lower contact point on therelay, the relay armature to the feeder wire,and so back to battery.Lighting of Signal Lamps

Now the bridging over between the firstrail and the sectioned second rail by thewheels and axles of the train closes anothercircuit, i.e., from the first to second railsthrough axle, from the second rail to thewindings of the coils of the relay in section 4,through the feeder and back to the battery.This relay is thus actuated, the contactleading to the third rail of section 4 is brokenand this section is rendered dead. At thesame time, the connection through the uppercontact is interrupted, and the green lightof section 5, which had previously beenglowing, is extinguished. The closing of the

relay passes current to the red lamp, andthis is made to glow until the train passesout of section 5, when No. 4 relay falls back,and everything is restored to its originalstate ready for the next train.

From this it will be seen that should afast following train be overtaking another,it will be repeatedly stopped in the sectionbehind that occupied by the leading train.

ti

TO2 N12RAIL

TO RED LAMP-0- TO GREEN LAMP

TO THIRD RAIL.,-

FROM BATTERY,1A FEEDER GABLE.

Fig. 3.-A perspective sketch of the relay.

Where stations occur, the trains, unlessthey are to run through, will be stopped bythe operator, and to do this he will have aswitch on his control panel with a wire run

to the relay of the section in which thestation is placed, say section 6. This willenable the operator to close the relay and socut off current from section 6 at the precisemoment when the train is in the station.Any following train will continue to rununtil it reaches section 5, where the signalsfor section 6 will be against it, and it willpull up.Relays

A scale drawing of the relays is given inFig. 2. In the foregoing, upper and lowercontacts have been referred to, but actuallythese are side by side and all three are madeof thin spring brass. The coils are onbobbins of thin sheet brass, each wound withabout 5 oz. No. 28 enamelled copper wire.The two are connected up in series andencased in thin sheet -iron to increase themagnetic effect. The cores are of soft iron,as is also the armature. The pivots of thelatter are formed by brass screws shouldereddown.

To pull the armature off the cores whenthey cease to be polarised, an adjustableweight formed by two knurled nuts isshown-two are necessary for locking pur-poses. Large terminal heads of brass maybe used for making up this weight. Therest of the details will be obvious from thedrawing, aided by Fig. 3, which is a per-spective view.

(To be continued.)

THESE notes deal with the usualmethods of accumulator storing aspractised to -day, together with some

information that has been acquired throughexperience. There are two commonmethods of storing, wet and dry, each ofwhich is divided into two subsectionsdepending on the exact technique involved.

The dry method seems the most enticing,since batteries so stored need not betouched for twelve months, but it is theleast satisfactory, and cannot be recom-mended. The battery is given a full chargeuntil voltage and specific gravity readingshave been constant for a period of one hour,then an over -charge of one hour is given.The cells are then emptied and the batteryacid stored for future use. When possible,remove the plates from the boxes, wash indistilled water and replace the separators,if of wood, with new ones. \Vash out thecontainers with distilled water, leaving theplates in the water. Now replace theplates, seal the containers, fill up withdistilled water, and leave for thirty hours,when it should be emptied. Allow it todrain for a minute and then seal the ventplugs. The battery should be stored in acool dry place.

Doubtful CellsThis method may be varied, especially

with cells whose condition is doubtful, bymerely emptying out the acid and replacingwith distilled water as before. Some autho-rities state that before cells are put intodry storage they should bA fully dischargedat the normal rate. This means that thebattery must not be short-circuited througha length of thick wire or left standing untildischarged before putting into storage.After fully discharging through a suitablelamp or other load, the cells are treated asunder the charged method. After twelvemonths the battery must be refilled with itsoriginal acid, or acid of the same S.G., andgiven a long slow charge at half the normalrate. If the battery is left as long astwelve months. it is generally found that thenegative plates have acquired a compositionresembling hard slate, and will neither takenor hold a charge. This is the one big

STORINGACCUMULATORS

disadvantage with these methods, and theyare not to be recommended except in thosecases where it is impossible to keep thebattery charged. However, before resort-ing to the above methods, the others shouldbe first thoroughly investigated.

There is yet one other method of treatinga battery before putting it into dry storage,which is considered the best, but it has thedisadvantage of damaging the positiveplates if these have seen much service.The cells are emptied and the acid replacedwith distilled water, which is left for twelvehours. The cells are then given a chargeuntil all gas freely, and the gravity remainsconstant, readings being taken every thirtyminutes. The plates are now washed indistilled water and then left in water fortwenty-four hours, when they are ready fordry storage as before.

Methods of ChargingThose who have faculties for charging

should adopt one of the following methods ;details of the actual charging methods areomitted, but if unfamiliar to the reader heis strongly advised to read " Accumulators,"by F. J. Camm, obtainable from Messrs.Geo. Newnes Ltd., 8-11 SouthamptonStreet, Strand, W.C.2.. Price Ls., or ls. 2d.post free. Arrange the batteries on a suit-able bench where they will not be disturbed,and where spanners and other tools are notLikely to get left or dropped on them andcause " shorts." The trickle -charging ratewill depend on the type of cell, but it maybe best found by a little experiment.Connect the cells in series, examine andcorrect the acid level, and test the gravity.Start charging, test the gravity each day;if the cells gas, then too much current ispassing, but if the gravity falls slowly, thenthe charging rate must be increased. Whena satisfactory rate has been determined, thecells may be left undisturbed, but shouldhave the acid level and gravity checked

each month. Before storing cells on tricklecharge, they should have had a full chargeimmediately beforehand.

The best method of storing cells is to givethe battery a full charge once every twomonths. Arrange the cells so that leadsfrom the charging panel may be easilyconnected, examine and correct acid level.etc., and then give the batteries a fullcharge. The cells may now be left for twomonths, but before charging again the acidlevel should be noted. If any cell is lowerthan the others, charge until it is againhealthy, or, if this does not bring it up,examine carefully, and correct the mistake.

Useful HintsTo the above notes several hints must be

added. Use only distilled water unlessyour tap water has been approved by thelocal Battery Service Station. Space allbatteries, and, where possible, arrange themon standard porcelain insulators, or, failingthis, on white porcelain tiles. Aftercharging carefully, dry the tops of each celland vaseline all connectors, terminals, etc.,and see that the vent plugs are not blockedup. For the hydrometer reading to be ofany real use, they must be tabulated as soonas taken, and then the performance of thecell can be told at a glance. Make up atable of a series of columns, and mount itover the battery bench on a loose board, sothat the attendant may carry it round withhim and enter up any readings of theparticular cells.

An article of this type would not becomplete without a few notes on storingnickel -iron accumulators. These cells canbe left for years either charged or unchargedwithout being damaged in any way, butif charged they will maintain the full voltageon open circuit for periods of up to twelvemonths and over, and then deliver theirfull capacity. It should be noted that ifthe cells have been given a recent charge thevent plugs should be unscrewed to allow anygas to escape. and then tightened up again,vaseline all terminals and connectors, alsosee that the cells are placed on a dry benchaway from lead -acid batteries. These notesapply specially to the Ni-Fs cells.



Fig. 1.-Lightly clean up the reversed face of the flange and, with an insidescrew -cutting tool, scribe the 1 f -in, diameter pitch circle as shown.

THE next parts to claim attention arethose forming the moving unit. Theyare the crankshaft, part 5 ; connecting

rod, part 7 ; piston, part 8 ; cam adapter,part 9, and sundry small parts connectedwith them.

Machining the CrankshaftAs the crankshaft is supplied in a

" roughed -out " condition, the final machin-ing can be straightway commenced. Fileoff the parting pip (if any) from the tail endof the blank and hold in the 3 -jaw chuck

LATHEWORK FOR AMATEURS

BUILDING GA 15 c.c.

SPKOKE PETROL(Continued from page 168 of the January 1935 issue)

Some provisionwill have to bemade for holdingthe shaft beforethe crank -pin canbe machined.Reference to thecrankshaft draw-ng (part 5) revealsthat the centre of

the pin s As off centre, and it will also benoticed that the bolt holes in the flange ofthe cam adapter (part 9) are arranged ona pitch circle of 11 in. diameter. This partwill then form a very convenient throw -plate and enable the pin to be machinedon the centres.

The centre hole in the cam adapter, ifnot already done, is reamed to 1 in. dia-meter and passed over the end of the shaft,still in the lathe, and a nut passed on withthe fingers, as seen in Fig. 3. Bring the tailcentre to bear in the centre hole, and adjust

Fig. 2.-.Showing the shaft mounted ready for turning the pinand finishing the front face.

by the lf-in. diameter portion, allowing theface to project about 1 in. clear of the jaws.Tap the end of the shaft true and tightenthe jaws well on to the work. Centre -drillthe end of the shaft, and support with thetail -centre.

Turn the shaft its entire length to withinA above 1 in. diameter. Further reducethe shaft to a similar amount over -1 in.diameter, stopping the cut 11 in. awayfrom the shoulder, and turn back for thethread to' - in. diameter so as to leavethe 1 -in. diameter portion 1 in. long. Takea light facing cut across the 11 -in. diameterportion and a second cut e in. deep, toform a boss 11 in. in diameter. This pro-vides clearance for the outer ring of theball -race. The shaft before finishing isseen in Fig. 2. Screw the thread on to thelathe, carefully fitting it to a standard -o-in.B.S.F. nut. Finish turning the }-in. and1 -in. diameters, leaving a couple of thou-sandths for final finishing with a verysmooth file. Ease the front end of bothdiameters slightly, so that the races pushon easily to within in. of the shoulders asshown in Fig. 2.

finely ground inside screw -cutting toolagainst the mark and scribe the 1} -in.diameter pitch circle with it by running thelathe, as is shown in Fig. 1.

Remove the adapter and divide the pitchcircle into six equal parts and carefully spotup the hole positions. Drill the holesslightly under No. 6 B.A. tapping size, andlightly countersink the mouth of one hole to60 degrees. The crankshaft can now betaken from the chuck, and with the shaftproperly supported in a vee-block, find thecentre and scribe a line TV in. above it onto the face of the crank -pin. Before scrib-ing, the shaft must be rotated to bring thepin in the highest position. Bisect the lineon the pin and spot up with care and drillwith a centre drill.

Machining the Crank -pinSelect a suitable carrier to hold on the

* in. diameter of the adapter and pass onto the shaft, arranging it so that the long

Fig. 3.-Taking a facing cut across thebalance weight.

for running, afterwards ocking the nut witha spanner. Take this precaution to preventmoving in the chuck whilst tightening.Turn the forward boss to 41 in. diameter fora distance of IA in. (plus a few thou.), tothe face of the flange, which must be cleanedup in any case. This boss must be smoothlyfinished to a goodrunning fit in the*-in. diameter holein part 3. Turn theflange over the topto exactly 1 -&-in.diameter, andreverse the adapteron the shaft.Lightly clean up thereversed face of theflange and scribe ashort line on itexactly j72 in. fromthe edge: Bringthe point of a

Fig. 4.-Showing thecrankshaft and cam

adapter.

boss is nearest the cranl; end, lightly lockingby means of a nut. The countersunk holeis arranged approximately in line with thecentre hole in the pin. Place between thecentres and get the back face of the crankplate running true, by slightly twisting thecam adapter on the shaft in the required


AprII, 1935 NEWNES PRACTICAL MECHANICS 325

OVIODEL TWO -

E NGINE TART HIBy W. H. DELLER

direction, and afterwards lock in position.Insert a small brass pad between the endof the screw and the work before lockingthe carrier. Fig. 2 shows the shaft mountedready for turning the pin and finishing thefront face.

Take a facing cut across the balanceweight to leave it in. in thickness and faceout as far as possible round the pin to leavethe web f in. thick. This is most con-veniently carried out with a holing tool, asis also the turning of the crank -pin itself.Reference to Fig. 3 will make the methodclear. Finely finish the pin to .374 in.diameter, leaving a small radius in thecorner. Continue the facing cut with asquare inside recessing tool and bore awaythe inside edge of the balance weight untilit is ff in. away from the inside edge ofthe crank -pin. This part of the machiningis now complete, with the exception ofturning the crank plate to size and drillingthe lightening holes.

depth of 1 in. isreached. Scribe ashort line withodd legs on eachside of the crank-pin in. fromthe edge ofthe crank plate,and drill a A -in.diameter hole onboth sides at centre distances off in. from theedges of the pin. A 11 -in. (or No. 5) dia-meter hole is drilled right through thecrank -pin and plate, and tapped halfwaywith a k -in. B.S.F. thread. Chamfer themouth of this hole on both sides, and alsodo the same to the other lightening holes.

Finishing the Cam AdapterFinish the adapter by holding it in the

three -jaw chuck on the if in. diameter sothat it runs true. Face the front of theflange to j in., and turn the boss to 1 in.

Fig. 6.-Adjusting the depth of the grooves.

After removing the cam adapter, gripthe shaft in the chuck by the 1 -in. diameterand turn the plate over the top to I fi in.diameter.

Centre the plate and drill a -{g-in. dia-meter hole down the shaft for a depth of

in. to the lip of the drill, and continuedrilling with a f -in. drill until a total

Fig. 5.-Scraping a small radius on the mouth of the piston beforeremoving from the chuck.

better not to rely upon the small chucking bossto machine the piston, but to grip the body ofthe casting in the chuck for the purpose.

Catch in the chuck and face back theskirt until the piston is 11 in. long fromthe edge of the head. Bore out to in.diameter with a slightly round -nosed tool,machining right up to the bottom edge of theinternal bosses. For the purpose of thesubsequent operation, see that a good finishis obtained in the hole, scraping a smallradius on the mouth before removing fromthe chuck (see Fig. 5).

Fig. 8.-Showing the partly assembled unit.

diameter and face. Mouth out the front ofthe hole to in. diameter to a depth of.3'2. in. Chamfer the front of the hole bysetting the tool slide to 45 degrees until thefront measures if in. diameter. Leave thiscountersink with a good finish, as it pro-vides a locking face for the special and conedlocking nut. Open the holes in the flange with

a No.43 drill, slight-ly chamfer on bothsides, and tap No. 6B.A. Fig. 4 showsthe crankshaft andcam adapter at thisstage.

Machining thePiston and Con-necting RodThe " con -rod "

and piston, parts 7and 8 respectively,are comparativelysimple jobs. It is

Fig.7.-Showing thefinished piston and

connecting rod.

There is one little job to do now, beforethe piston is finished, namely, drilling andtapping the piston ring retaining the screwhole, which if left until later, cannot besuccessfully accomplished. Scribe a line onthe side of the piston barely 14 in. up fromthe bottom edge and drill and tap a No. 6B.A. hole through towards the centre.Turn a peg in the chuck and polish so thatthe piston will " wring " on to it, using alittle oil to prevent seizure. Turn andpolish the piston on the outside diameterto 1 in. and turn the ring grooves. Thiscan best be done by grinding a partingtool to .0015 in. wider than the rings andfeeding straight in. The depth of thegrooves should be such that when the ringis in the groove (see Fig. 6), and a rule laidalong the piston, there is a clearance of A in.between the rule and inside edge of the ring.The tapped hole should come in the middleof the centre ring -land.

Saw off the chucking piece and file upthe head of the piston. Mark off for thegudgeon -pin holes at a distance of if in.up from the bottom opposite to the internalbosses. Lay the piston on a vee-block,find the centre and set the baffle on the head



level with the surface plate. Scribe acrossthe lines previously made and make acentre dot where the lines intersect on bothsides Centre -drill on each side and drill aa -in. hole through the bosses. As theseholes must be in line, the drilling is bestcarried out in the lathe with the pistonsupported on the tail centre. Followthrough with a No. 19 drill, and open outto in. diameter with a parallel reamer,but do not let the " lead " of the reamergo right through both bosses. Use thepiece of steel supplied for the pin as a gauge,and make the fit of the hole such that thesteel taps lightly into the back hole.Should a suitable reamer not be available,a drill may with care be used in the samemanner.

The Gudgeon -PinThe gudgeon -pin (part No. 11) is, accord-

ing to the specification, made of case-hardened mild steel, but the materialactually supplied is silver steel, so that ifhardening is thought necessary, it must bequenched and tempered to a very darkstraw. Pads (part No. 12) are fitted tothe pin. Small snap head copper rivets maybe used, but if turned from copper or brassrod, are best made on the end of a shortpiece and driven lightly into the pin, cut andfaced off afterwards to make the total lengthover the pads measure slightly under 1 in.,the ends being domed to in. radius.

A small pin requires fitting in the tappedhole in the piston. This must fit tightlyand therefore a portion of a standard screwis unsuitable. Ease a piece of On. diameterbrass rod down to 110 in. diameter and runon % in. of No. 6 B.A. thread, adjusting thedie to give a tight -fitting thread. Screw

into the piston and cut off and file downflush with the surface, then with a fine safe -edged file, flat off the pin on each side whereit projects in the ring grooves to leave itproud of the sides of the centre land byA in. The fitting of the piston rings isleft for the moment.

The Con -RodThe connecting rod (part No. 7) is made

from i-in. square Duralumin bar. Mark acentre line lengthwise on same and drilland ream a 1 -in. diameter and an if -in.diameter hole at a centre distance of 211r in.Machine up correctly the I -in. bosses, asshown in Fig. 10, and treat the small endin a similar manner. Remove the metalbetween the bosses by sawing and filing, andadopt the same metho I for shaping the rod.After facing the bosses down to in. across,central with the web, radius one side of thefin. hole to suit the crank -pin. By theway, the pin must project slightly abovethe face of this boss. Provision is made forlubrication by drilling a hole through thebottom of the boss in the big -end and filinga A slot across the boss in the small end.Fig. 7 shows the finished piston and con -rod. A special }-in. B.S.F. brass screw(part No. 10) retains the big end of theconnecting rod, and as it is a simple partto make, no comment, beyond the fact thatthe thread should be a good fit and thehead screwed down in close contact withthe end of the crank -pin, is necessary.

Lapping the CylinderTake a short piece of 1 -in. diameter

bright mild steel about 4 in. or 5 in. long,face up one end and ease down if necessarywith a fine file to the exact size. Cut a

series of shallow annular grooves along theprepared portion, about in. apart, withthe nose of a front turning tool. File asmall radius on the end of the bar. If thelap will not pass into the cylinder liner, easeit slightly until the front just pushes in.Charge the lap with very fine cutting com-pound such as rouge and oil, run the latheslowly and push the cylinder backwardsand forwards until the bore is polished. Thisoperation requires care to prevent seizure.

Assemble the piston and connecting rodand lap the piston to the cylinder by hand.

Wash both parts in petrol and proceedwith the fitting of the rings. Ease the endsof the ring if necessary, to permit them topass into the mouth of the cylinder. Therings will, of course, go in without filing,but in all probability the adjacent endswill not lie flush. Carefully fit until theydo, allowing the ends to butt together,without clearance. Next file a small notchin each ring to fit over the pin, fitted in thepiston to prevent the rings from turning.These notches should be made in suchrelative positions that the gap in each ringwill be spaced from the other at 180 degrees,also so that the ends of both rings do nottravel over the ports. Lightly lap therings to the cylinder by hand. After thishas been done it will be noticed that thereis sufficient clearance between the ends ofthe rings.

There is just one point regarding theconed retaining nut (part 19) for the camadapter. See that the tapped hole isabsolutely true with the coned surface.Fig. 8 shows the partly assembled unit.This brings the engine approaching thepoint where final assembling may becommenced.

THE world is slowly realising that thereis more potential wealth and pros-perity and happiness in a lump of coal

than in an ingot of gold.Fifty years ago or even less, coal was

burnt in the ordinary grate without athought of what was going up the chimneyin smoke. Valuable chemicals which are nowbeing collected and " bottled " went up intothe skies and blackened our atmosphere.

To a certain extent this is still so, but weare being gradually educated to see howmuch of our national prosperity depends onthe complete scientific exploitation of ournatural resources.

Very few people have any idea of the vastnumber of entirely different substanceswhich can be derived from coal. Take gas -2l tons of it can be extracted from 100tons of coal. From the same 100 tons ofcoal we can get 1,000 gallons of tar, enoughto make miles of road surface.

From the black tar also come a number ofdyes. Coal tar, too, is the base of one of theeffective remedies for diseases of the skin.

Main By-productsFrom what remains of the carbonised

coal we get graphite, coke, ammonia andthe residual flue dust. These are the mainby-products, and once they have beenextracted and isolated the scientist gets towork and starts to separate them to thelast ounce.

Every time you burn coal in the domesticgrate you lose 75 per cent. of the heat andevery one of the above by-products go upthe chimney. It is about as extravagantand foolish as burning furniture.

The coal industry of this country is in abad state, and things do not look like im-proving for some time to come. Normally,vast quantities of coal are used for ironand steel production, but this has becomegreatly reduced in the last few years. Our

COAL-Some I

Interesting Factscoal magnates are at last realising that ifprosperity is to be restored to the coalindustry every single ounce of that coal mustbe utilised.

Every year we import over 2,000,000,000gallons of foreign oil and petrol, partly forour ships and partly for our cars. If wewere to utilise coal in the way it should beutilised, we could supply all our needs inthis direction.

Nearly 200 substances have been isolatedfrom coal at the present time, including theheavy oil with which nearly 1,000 of ourships are driven.

Coal DerivativesWho would think that when we develop

our snaps we are using coal -derived chemi-cals and that when we have a headachewe can take a coal -derived aspirin tablet tocure it ?

But this is only a beginning. Our carsare driven by benzole, and the roads theyrun on are made with tar, both importantcoal by-products. We write with coal -derived graphite pencils, cook our mealsand heat our rooms with coal -derived gas,we sit in the cinema and the image we watchon the screen is lit with coal -derived carbonarcs, the ice which cools us in summer ismade by coal -derived ammonia, our daintyperfumes are made from coal -derived gas,the houses we live in are made from coal -derived blocks.

The dirt in our skies is another importantaspect of this vital problem. More thanhalf of the three -year -old children in thiscountry have rickets because they are

robbed of sunlight by the smoke pall whichhangs over our cities.

FogsDuring heavy fogs caused by smoke

traffic is disorganised. In twenty-sevendays of fog during recent years the buses ofLondon lost 400,000 working miles. Weinsist on clean food, clean water, bodilycleanliness, yet our breathing tubes andlungs are blackened and polluted with dust,soot and sulphuric acid.

We protest against the vandalism ofwriting on the sky-and allow industries toblot out the sky writing.

Consider for a moment the matter pouredforth from coal -burning chimneys. It wassaid recently that the city of Manchesterburns 3,000,000 tons of coal a year, only750,000 tons of which are used fur domesticpurposes. There are 1,100 factory chimneysand 150,000 houses in that city con-tinuously discharging into the air a productof the incomplete combustion of thesemillions of tons of coal. The result is that20,000 tons of solid matter falls into thecity area, with tar and acid, to the amountof 75,000 and 200,000 gallons respectively.

Because of this condition of soot, Man-chester spends on the small matter oflaundry bills a quarter of a million poundsa year more than it would spend if its airwere as clean as that of Harrogate.

Many prominent industrialists areawakening to the urgent need for a scientificcoal industry. The more extensive use of coaby-products will permit of more economicmanufacture of the main products, gas andcoke ; and this, in turn, will benefit in-dustry, particularly the iron and steel in-dustry, which annually consumes largequantities of metallurgical coke. Byburning raw coal millions of pounds worthof valuable by-products literally go up ourchimneys in smoke,



"PLASTICS" AND THEFKUSESAn account of the new synthetic resins. Progress in the next ten years will produce strong

light materials which will influence many branches of engineering and construction.

ASPECIAL section of the exhibition ofBritish Art in Industry is devoted toplastics mouldings. A whole room is

panelled with cameos of these new materials.Yet ten years ago plastics were scarcely onthe market. The rise to importance ofthis remarkable group of substances willgo on rapidly. They are destined to havea very great influenceon the course of every-day civilisation in thecourse of the next tenyears.

As yet the mostambitious plastic pro-duct in familiar use isa wireless cabinetpressed out in onepiece. But plasticmanufacturers are al-ready prepared tomould the completeinterior furnishings ofa house, from the doorsand wall panellings tothe furniture and bath-room fittings. Themost remarkabledevelopment is thenew crystal-clear plas-tic which is illustrated.This is assured of animmediate outlet inthe replacement of present-day safety glassin motor cars. As it is at least as strongas cast-iron and can be moulded to anyshape it should solve the problem of equip-ing stream -lined cars with large windowswithout interfering with the stream-lined curves. The strength, lightness andcolourful durability of plastics have every-thing to recommend them to the car de-signer, and even to the aeronautical engineer,in their search for light materials whichwill give high performance at low horse -powers.

What are Plastics ?Speaking in the most general terms, a

plastic is any sort of resinous or gummymaterial which on being cast, pressed ormoulded, sets hard and firm. Thus shellacis classed as a plastic. So are artificial silkand celluloid. But to -day the term isreserved for certain types of artificial resins,the first example of which was bakelite.Bakelite was first made by a Belgianchemist, Baeker, in 1906, by heating to-gether strong formalin and a substanceobtained from coal tar, called phenol. Hefound that his resin became hard and firmwhen it was heated and pressed. Thematerial had a limited use during the post-war years for making electrical apparatus.Its advantages were quickly realised, andsoon chemists got on the track of othersubstances like it. The business really gotunder weigh in 1924. ' Since then onemeasure of its progress is the thousands ofpatents which have been taken out toprotect the manufacture of newly dis-covered plastics.

A few of the groups of these substancesare the formaldehyde -urea, the benzyl-cellulose, the vinyl -acetate and celluloseacetate plastics. These are names indicat-

ing the chemical origins of preparation.Rubber forms the starting -point of a groupof plastics. Investigation goes rapidlyalong lines which are designed to find newplastics of greater strength, transparencyand resistance to heat. A plastic has evenbeen produced to replace the natural gumused for chewing gum.

sometimes used. Heavy pressure and steamheat cause the resin first to flow and then tochange into a smooth hard tenacious sub-stance. Pressure is left on for about aminute to effect the cure, and then thepress is opened and there in the mould liesthe brightly coloured article. A shortannealing process may follow and feather

edges from the " flashoff " of the mould mayhave to be machinedoff. After that thearticle is quite readyfor the market.

The control of themoulding needs a prac-tised hand. The pres-sure on the press mustbe exactly controlled.The weight of thecharge has to be justright otherwise themoulding is not clean.The mould and the diemust be bright andclean otherwise themoulding is stainedand marked. Stainlesssteel moulds and diesare therefore used. Thetemperature of thesteam heating controlsthe polish and tenacity

of the moulding. Finally, experience isrequired in mixing different colouredpellets and powders to get the right shadesand runs of the mottlings and marbellings,which are a feature of plastic mouldings.

Features of PlasticsThe behaviour of a plastic to heat

depends on the resin from which it has beenpressed. Some soften and run just abovethe boiling point of water. But others arenot affected by heat until they become sohot that they char. None of the modern

ones are inflammable likecelluloid. Plastics withevery fresh discovery in-crease in strength. Theyare at the present day some-where round the cast-ironmark. One called vinylite,a milk -white solid, made by

heating two chemi-cal liquids withsoda, needs a ham-mer and anvil tobreak it. It isused for gramo-phone records as

A display of unbreakable table ware, made of - Beat! urea-fo rmaldehyde plastic.

How Plastics are MadeThe first step in the manufacture of a

plastic is to make the resin. This is aprocess of chemical synthesis in whichliquid substances are mixed together andheated. The chemist calls it a condensa-tion. The result is a thick, syrupy liquid.This is then evaporated under vacuum togive a stiff gum. At this point a " filler "is mixed in and colouring matter, if desired,is added. Fillers are usually either woodmeal or cotton lint. The mixture of gumand filler is then completely dried andafterwards ground to a very fine powder ina ball mill. This powder is then sentforward to the mouldingpresses in powder formor as lightly pressedpellets.

The moulding processpresses the resin powderinto the form of thefinished article, and setsit hard and firm at thesame time. This settingis called the " cure."The powder or pelletsare fed to a steel mould,and a die is closed on themould. Between dieand mould the shape ofthe finished arti-cle is formed. Themoulds are steam -heated, and thedie is forced home by hydraulicpressure. Pressures as high as200 tons per square inch are

A blade mixing machine formixing resin syrup withfillers and colouring matter.



One of the most interesting examples of the beautifuleffects which can be obtained by engraving the newtransparent plastic material. This is a dodecahedron,with a hole in the top surface which is facing thecamera. Through this hole is seen a pentagon facingin the opposite direction, with a star engraved upon it.The star is seen direct through the central hole, butthe stars which appear to be engraved on the otherfacets are actually seen by reflection and refraction.There is only one star though six appear in the

illustration.

its toughness gives an almost indefinite life tothe fine grooves of modern electrical record-ings. Others are extremely flexible, andcan be produced in thin transparent sheetsgiving the better quality cellophanes. Ifthe original resin is hot -rolled on to cottonfabric, brightly coloured transparentmaterials are produced, which are indistin-guishable from oiled silk. Cellulosic paintsand lacquers represent another large classof plastics, which are brilliant, hard-wearing and oilproof. You have only tonotice the screw caps of bottles and tubesin a chemist's shop to realise how much

plastics have replaced old-fashioned corksand therefore how cheap they are to pro-duce. Wherever you see articles made ofmaterials which you would vaguely callvulcanite, celluloid or bakelite you may befairly certain that it is made of one of themore modern plastics.

ColourOriginally one of the troubles with

plastic resins was that they turned brownor muddy with age. Research has over-come this difficulty. The picture of theplastic crystal shows that in this direction

perfection has been reached. The colour-lessness of the modern plastic and itsstability to light permit the use of dyes andfillers which give such shades as clear jadeand rose quartz. Effects running fromopaque to translucent and transparent canbe obtained with the utmost certainty.Even the high lights of opal and onyx canbe imitated.

In plastics, science has sprung a group ofmaterials on the world which are morewonderful than the most inventive of scien-tific prophets have dreamt about. By some,the near future is heralded as the Plastic Age.

A batch grinding ball mill. Dried, filled resin is rolled over and over inside this with hard sledballs which crush it to a fine powder.

HATCHING EGGS BY AIR FROM ENGLAND TO AUSTRALIAAN experiment never before attempted,

that of sending a sitting of hatchingeggs for 12,800 miles by air, was

carried out in connection with the recentdeparture of the first air -mail service fromthis country to Australia.

The eggs were consigned by Captain theHon. C. K. Greenway (now Lord Green -way) from his poultry -farm at StanbridgeEarls, Romsey (Hants.), to Mr. F. P. Finney,of the Rhode Island Red Club, Sydney,New South Wales. On their first stage theeggs were flown from London to Paris.Then came a train link to Brindisi, andafter this an air voyage across the Mediter-ranean in one of the big Imperial Airwaysflying -boats. From Cairo the load went onabove the desert to Baghdad, and on downthe Persian Gulf to Karachi.

Across IndiaAcross India the stages were flown in

one of the monoplane air -liners operatedby Indian Trans -Continental Airways, anassociated Company of Imperial Airways.

From Calcutta the flight continued toRangoon and Singapore; and then oneastward over fresh air links to PortDarwin and Brisbane-these new sectionsfrom Malaya to Australia being operatedby Qantas Empire Airways, anotherassociated company of Imperial Airways.The consignment of eggs reached Brisbanetwelve and a half days after leaving London,as compared with a journey of forty-five

days had they gone by land andsea transport, representing asaving of thirty-two and a halfdays. From Brisbane they con-tinued to Sydney by rail, beingdelivered to Mr. Finney a fewdays later. He immediatelyexamined the consignment andfound it in perfect condition,not a single egg having beendamaged in transit.

This first consignment ofhatching eggs by air fromEngland created immenseinterest in Australia. Photo-graphs of the eggs, and of thebox in which they travelled,appeared in the Press, with fullaccounts of the experiment.

Mr. Finney, the recipient ofthe eggs, has since communi-cated with Qantas EmpireAirways, and also with LordGreenway. In one letter, afterpromising to report further asto the results actually obtainedin the hatching of the eggs, hesays : " This experiment hascreated a ' stir ' everywherethroughout Australia, and Ifeel personally that it will open.up and develop the importingand exporting of hatchingeggs to many parts of theworld."

Experimenting with a new type of Land Yacht.

II



ELECTRIC LIGHTINGFOR OVIODELSATHOUGH light is the most funda-

mental controlling factor in all humanactivity, the science of lighting has

been for many years the most neglected ofall. It is only recently that the importanceof properly applied lighting has beenrealised and steps taken to ensure its pro-vision. This tendency has been reflectednot only in the more correct light-ing of ordinary models, but in thewidespread production of modelsdesigned solely to show lightingeffects.

Model lighting may be dividedbroadly into three classes ; firstly,exterior lighting, either to show upthe model to its best advantage, orto represent natural lighting in thecase of a scenic model ; secondly,the reproduction in a model of theactual lighting systems present inthe prototype; thirdly, the use ofmodels definitely designed to showthe effect of a new lighting systemin a proposed building. Generallyspeaking, the first two applicationsalone concern the average model-maker, the third is the provinceof the architect and professionalmodelist.

A Model LocomotiveFew constructors realise the im-

mense improvement that may beeffected upon a well -finished modelby means of properly appliedlighting ; to take a common in-stance, that of a locomotive. Thisis often housed in a glass case orupon a pedestal, and the ownerusually relies upon the general roomlighting for illuminating his model,with the result that the most im-pressive parts, the brightly polishedmotion work, are left in semi-darkness by the shadowing effect ofthe running boards. It is possibleto obtain for a few shillings, tubularlamps about 10 in. long and less than1 in. in diameter, complete withreflector for use on the house mains. Oneof these lamps mounted on either side of themodel at the bottom of the case will causethe usually obscure parts of the locomotiveto stand out with a clearness and sparklethat will astonish even its builder. Thistreatment, w i t hvariations, isapplicable to

WRITEINTER/OR

PLATEDSPUN ORHAMMERED CRP

most models with great success. Moststandard high -voltage lamps are availablewith blue -tinted glass bulbs known as" daylight blue " finish these produce a

Fig. 1.-A striking photograph of a scale model ofdesigned by one of our contributors, Mr. E. W. Twining.

constructed on the diorama principle.

very white light which shows up the whitemetals with a far greater brilliance than themore yellow light from the usual type oflamp.

Probably the greatest achievement in theway of scenic model lighting was the

ranoramic working model of theattack on Zeebrugge at the British

GREEN OR GREYEmpire Exhibition in 1925. Herethe representation of a sunset

INTER/OR and the gradually appearing starsequalled anything to be produced

Fig. 2. -A by the lavish lighting equipment ofstandard corn- a full-size theatre.mercial reflector.

A Model of BournemouthA more modern instance is the

large model of Bournemouth onview at Waterloo Railway Station.This model, which is probably the

Fig. 5.-A cut-offopal bulb used as a

hanging fitting.

GLASS HELDBY SPRING

CLIPS

Fig. 4.- Ause for a cut-off standardopal lamp.

Bournemouth,The model is

How the appearanceof models may beimproved by properlyapplied lighting effects.

most magnificent of its kind everproduced, represents in two sections oneand a half square miles reproduced in thecompletest detail. It is constructed on the

diorama principle, that is, the scalediminishes from front to back inorder to produce perspective untilit merges into the backcloth. Thelighting system is housed behind apelmet in the roof of the case andconsists of standard gas -filled lampsin a trough extending the length ofthe case ; the trough aperture iscovered with diffusing glass of atype known as muffled glass. Sixty -watt lamps are used in three setsof fifteen, comprising white, orangeand blue bulbs to give effects ofdaylight, sunlight and moonlight.Change of effect is done by amotor -driven flasher which causesa gradual change -over by extin-guishing the lamps of one colourone by one while those of the nextcolour are switched on one by one ;this device obviates the need of aresistance dimmer. Fig. 1 givessome idea of the wealth of detailpresent in this model.

The branch of lighting whichchiefly concerns the average modelistis the provision of scale lighting asa finishing touch for any type ofmodel. Difficulty is often foundhere owing to unfamiliarity withthis sort of work, lack of know-ledge of the appropriate prototypefitting and the paucity of commer-cially obtainable light -sources ofscale appearance. The cheapestand most easily obtainable smalllight -source is the so-called flash -lamp bulb ; this unfortunately isdifficult to work into any small scaleon account of its large screw cap.

Interior LightingLighting of interiors divides itself into

three sections ; direct lighting as is usedfor workshops and industrial purposes ;general diffusing fittings used in offices,public buildings and domestic interiors ;and what is known as architectural lighting.The first two of the above systems comprisedefinite hanging fittings, usually suspendedon wire, chain or conduit, and presentthe greatest difficulty to the modelist.

For industrial interiors the usual typeof fitting is that known as the StandardDispersive Reflector. Fig. 2 shows thespecific profile of this, and it may readily

.SOCKET

CEILING

KINSPLATEDBAND Fig. 3.-

Using anopal buslampfor flushfittings.



be made up from thin sheet metal. It isnecessary for all model fittings of thisnature to be designed around the intendedtype of lamp in order to accommodateits socket. To be strictly accurate aspherical bulb should be used in theseindustrial reflectors, and a lamp manu-facturer's catalogue will reveal severalkinds of spherical bulb lamps ranging from

in. diameter to 1 in. ; the leading firmsof model suppliers list lamps as small as

in. diameter.The diffusing fittings present more

difficulty as they are made of glass, a veryintractable material to the engineer. Itis therefore necessary to adapt standardforms of glassware, and there is scope forconsiderable ingenuity in this direction.Fortunately the modern tendency is to-wards extremely simple spherical forms ofopal glass, and this considerably simplifiesthe model -maker's problem. In modelsof 1 j in. to the foot and larger, sphericalopal 12 -volt lamps, as used for interiorlighting of vehicles, can be made directlyinto the most effective flush mountingfittings, as shown in Fig. 3. A simplealternative where the 12 -volt supply isundesirable is to take a burnt -out 40 -wattstandard opal lamp and cut off the lowerpart of the bulb ; this may be utilised asshown in Fig. 4, and lighted by any typeof lamp thought desirable. These cut-offopal bulbs can also be made into a hangingfitting as in Fig. 5, which is self-explanatory.These full-size lamp -bulbs may be cut offby tying a length of string around therequired plane of fracture, soaking in petroland igniting ; this method is only applicableto gas -filled lamps, but the vacuum typeshatter dangerously.

Small ModelsThese adaptations of full-size lamps are

only applicable, as was pointed out, tolarge-scale models ; for smaller sizes it

will be necessary to obtain smaller spheres.These may be found in the form of variousbeads or glass ornaments ; alternatively,

Fig. 6.-A model designed to show the effect of flood-lighting.

there are a number of firms who will makeopal glass spheres to any size for a verymoderate sum. Another modern tendencyis to make lighting fittings from flat glass

panels set in metal frames. Nothing issimpler than to model these from small -section brass angle and strip. Either thinglass or celluloid may be used for thepanels, and rendered obscure by meansof the crystalline lacquers now available;it is difficult to obtain opal glass sufficientlythin for the purpose. Countless suggestionsfor the design of this type of fitting may beobtained from modern catalogues.

Architectural lighting is the term appliedto lighting which is built into the structurein the form of wall panels, lintels, skylights,etc., and is capable of being reproduced toany scale as the size of lamp used is im-material. So unlimited are the possibilitiesof architectural lighting that it may wellbe made the subject for a special branch ofmodel -making ; the major point to beobserved is that the lamp spacing behindthe glass should be adjusted to obviate anypatchiness in the brightness thereof.

Pendant FittingsThe use of models designed to show

lighting effects is illustrated in Fig. 6 ;this represents a building to a scale of in.to the foot, and is designed to show sevendifferent methods of floodlighting.

When pendant fittings are being modelledit is often the practice to hang them upontheir wires in accordance with full sizeprocedure. This should never be done,since the weight of model fittings is in-sufficient to keep the wires straight. Thewires should always be run through small -section tube to simulate conduit, which isin accordance with the best recommenda-tions, and makes a neat job.

Finally, it is not enough to think that afew flash -lamp bulbs scattered about amodel represent model lighting ; the exactmethod of illuminating the prototypeshould be ascertained, and that scaled downwith as much care as the rest of the model.The result will inevitably repay the troubletaken.

AN Imperial Airways pilot, Captain0. P. Jones, has recently completed1,000,000 miles. He first entered

aviation in 1917, when he underwent acourse of flying instruction at Shoreham.Captain Jones then became a service pilot,and put in approximately 550 hours' flyingin many different types of aircraft whilewith the R.F.C. and R.A.F. Then, resigningfrom the service, he started a joy -ridingbusiness of his own.

3,116 Passengers in Three DaysSubsequently, for some time, he was

with Mr. A. J. (now Sir Alan) Cobham, andthen flew as a pilot on the early Continentalservices, joining Imperial Airways on itsestablishment in 1924. Captain Jones hashad the honour, several times, of pilotingair -liners in which the Prince of Wales hasbeen a passenger. On one occasion, whilegiving demonstration flights in Scotland,Captain Jones took up 3,116 passengers inthree days. Another remarkable record as apilot is that of Captain F. Dismore, ofImperial Airways, who has now been flyingregularly for twenty-one years, his airexperience dating back to before the war.He was also flying constantly during thewar ; while he has been engaged ever sincehostilities ceased in piloting commercialaircraft. Captain Dismore gained hiscertificate of proficiency as a pilot as farback as 1913, and his air career since thenis believed to have established a record forcontinuous flying over a long period ofyears.

MASTER -PILOTSOF THE AIR

Twenty-one years ago, when CaptainDismore first began to fly, he was piloting acrude, box -type biplane driven by a single50-h.p. engine and carrying a pilot and onepassenger. To -day, illustrating twenty-oneyears of progress, he flies as Commander ofair -liners which are driven by four enginesdeveloping a total of more than 2,000 h.p.and which accommodate as many as forty-three people-thirty-nine passengers and acrew of four. Among the other veteranpilots of Imperial Airways a well-knownfigure is that of Captain A. S. Wilcockson.Joining the R.A.F. at the beginning of1917, Captain Wilcockson completed 580hours of flying before demobilisation in1919. For some months after that he actedas pilot on the official air service whichcarried mails from Folkestone to our Armyof Occupation at Cologne. Then he beganflying on the pioneer commercial air linesbetween London and the Continent, sub-sequently joining Imperial Airways. Cap-tain Wilcockson has gained distinction as atest -pilot as well as an air -liner Commander,having carried out much of the early test -work with slotted -wing aircraft. Thenumber of hours he has spent in the airnow total 8,991.

Another veteran of Imperial Airways is

Captain W. Rogers, known to his manyfriends as " Rodge." After seeing warservice with the R.A.F., Captain Rogersbecame an airway pilot in 1920, flying thetwin-engined machines which were the fore-runners of the giant four-engined craft ofto -day. Now the number of hours he hasspent in the air stand at 7,880.Two Veterans

Two more of these veterans of the air areCaptains H. H. Perry and H. J. Horsey.The former, after a large amount of flying inthe early days of civil aviation, joinedImperial Airways in 1927, and his flyinghours now reach a figure of 7,137. CaptainHorsey, who is an expert in handling flying -boats as well as big multi-engined land -planes, has now spent 6,088 hours in theair. At the present time approximatelyseventy pilots, captains and First Officers,are in the regular service of Imperial Air-ways, flying on the European and Empireroutes operated by the company. Whencommercial flying began, just over fifteenyears ago, the first air -line pilots wererecruited from the official CommunicationSquadron which, during the last stages ofthe war, had been flying with importantofficials between London and the Continent.Each of these airmen was a master of hisart and, as the number of airway pilots grew,the wonderful spirit of those first men, andtheir fine attitude towards their calling, washanded on to those who followed them, theresult being that the air -line pilot of to -dayhas a great tradition to live up to, and isdoing so worthily.



A photograph of the finished model.

THE High -Speed Fury is a developmentof the ordinary Fury, and althoughthe two machines are very similar, the

High -Speed Fury has an even better per-formance than its predecessor. It has aspeed in excess of 230 miles per hour at15,000 ft. and a really phenomenal climb.Two Vickers guns are fitted under thefuselage and fire along the grooves in theengine cowling, and through the propeller,the Constantinesco gear controlling thefire to prevent the stream of bullets hittingthe propeller.

The differences of the two Furies can beeasily seen either on the ground or high inthe air, the High -Speed Fury having wheelspats and also a smaller wing area, obtainedby tapering the leading edge of the topplane and trailing edge of the lower.Models of the ordinary Fury can be madeto the sketch dimensions, leaving off thespats and keeping the edges of the planesparallel.

The photograph shows the High -SpeedFury. The model can be supported in mid-air with black cotton and ' shot " in anydesired position. The propeller should, ofcoarse, be removed, replacing it with a discof thin celluloid in order to get the effect ofa revolving prop.

The List of WoodsHere is the list of the various parts and

the sizes of the pieces of wood from whichthey are cut.

The dimensions in the panel include suffi-cient wood for insertion into holes wherenecessary.

Start off by making the spinner andpropeller boss from +-in. dowel rod. Thetaper can be cut with a chisel and thenfinished off with sandpaper. Pass anordinary pin through the centre of thespinner and place it in position at one endof the piece of wood from which the fuselagecan now be cut. The spinner acts as aguide for the correct shaping of the frontof the nose. The pilot's cockpit can becut out, the two gun slots filed out, and thesix small holes on each side of the enginecowling should be drilled. Next fit thetail -piece and the rudder, which may bekept in one piece and a deep score made oneach side to represent the hinge (as it canbe separated and hinged with pins as de-scribed in No. 1 of this series). The rearplane and elevators should now be cut outand fitted, a pin passed through the fuselage,and its head cut off, and so into the ends ofthe rail -pieces, making a more satisfactoryjob than by gluing. The tail -piece struts(a pair on each side) should also be fitted,these helping to locate the rear wing on thelevel. The tail skid, which is fragile, maybe left until later.

Next cut the lower wings and pin andglue them to the fuselage. Drive a hole in

SCALE MODEL AIRCRAFT No. 3

cfL SCALE MODELHIGH-SPEED FURY

The third article of a series dealing with scale models of most of thepresent-day aeroplanes

each wing for the reception of therear interplane struts, but do notfit at the moment.

Now make the top plane, eithercarving out the underside slightly or by wet-ting the wood and bending it under pressuretill dry. Note that the leading edge of thetop plane tapers away to the tips, whereas

LIST OF PARTSLong. Wide. Thick.

in. in. in.Fuselage . 5.5 e-75 1.05Tail and rudder . . 1.2 1.3 0.125Rear wings and elevators -

two . . . . 1.2 0.95 0.125Top plane . . . 7.2 1.2 0.15Bottom plane -two . . 2.7 1.1 0.15Wheel spats -two . . 1.0 0.4 0.25Shock absorbers (under-

carriage) -two . . 1.1 0.25 0.125Axle strut . . . 2.2 0.1 0.05Undercarriage rear struts --

two . . . . 1.7 0.05 0.05Centre inter -plane struts -

four . . . . 1.0 0.1 0.05Centre inter -plane struts -

two . . . . 1.0 0.05 0.05Inter -plane struts . . 1.6 0.1 0.05Tail -plane struts -four . 1.0 0.05 0.025Radiator . . . 14 0.55 0.35Tail skid . . 0.75 0.05 0.05Propeller -two . 1.2 0.2 0.1Prop -boss and spinner . 0.5 in. diam.

dowelWheels -on disc . in. dlam. 0.2

the taper on the lower plane is on thetrailing edge.

The AileronsThe ailerons, which are on the top plane

only, can be marked or separated as forthe tail plane. Drill six holes through theplane for the two rear inter -plane struts andthe four fuselage -cum -plane struts. Holesmust be drilled in the fuselage for thereception of the struts. Then glue thefour shorter struts into the fuselage andpush the top wing over the ends, seeing

2

1111111[1

Scale Drawingsof the modelHigh -Speed

Fury.

that the glue makes a good joint. As theangle which these struts make to the wingand the fuselage is wide, care must betaken in fitting, but the wood, being thin,allows them to be bent. Slide the rearinter -plane struts through the holes in theupper and lower planes and glue them in.Now set the angle of the lower planesand see that the gap is correct and equalon both sides, whilst the glue is still wet,and then place aside to set hard. Thefront inter -plane struts and the two centrecross struts are carefully fitted and thenglued in position, the other struts beingample to hold everything rigid.

The under -carriage can now be fitted.The two wheel spats are solid and the axlestrut passes through both. The wheelsare sections cut from one complete wheeland are glued to the underside of the spats.The two shock absorbers can be cut andshaped, or a thinner piece of wood used, theupper ends being wrapped with bands ofgummed paper to obtain the necessaryshape. The upper ends of the shockabsorbers are sunk and glued into thefuselage, the lower ends being trimmed offto size after fitting. The spats and axlestrut are then glued to the ends and the tworear under -carriage struts fitted.

The RadiatorThe radiator can now be cut to shape and

its surfaces grooved to imitate the coolingtubes. This is glued to the under -surfaceof the fuselage, between the under -carriagestruts.

The propeller is made in two halves, eachpiece being glued into a slot filed across thespinner.

The fastenings at the lower end of theinter -plane struts are built up with plasticwood or putty.

The model is now ready for painting.The fuselage and wings are silver lined out

4

ScA.Le. I - 50

with blue, standard R.A.F. icolours.Aluminium paint can be used all over,but that part to the rear of the cock-pit can have a little colour added,quite a small amount to make achange from the front, which in theprototype is all metal, whilst the rearis fabric -covered. The identificationdiscs are painted on the top of theupper plane, the under -sides of thelower plane and the sides of the fuse-lage, the blue ring being the outer, thecentre red, and the magpie white.



A Review of the Latest Devices for the AmateurMechanic. The address of the Makers of the items men-tioned can be had on application to the Editor. Please

quote the number at the end of the paragraph.

A Lawn Mower Sharpener

THE carborundum lawn mower sharpenershown herewith consists of a sturdy

rust -proof steel, curved top and bottom, soas to fit over the cross bar of the mower.The sharpening side is faced with a sheet of

A carborundum lawn mower sharpener. No toolsare required when using it, and there is no need to

remove the mower wheels, reversing cogs, etc.

clean, %at -cutting, abrasive cloth. Thehard, sharp, tough aluminous grains, withwhich the cloth is coated, quickly and easilycut a keen edge on the mower blades. Byreversing the sharpener from time to time,you equalise the wear on the cloth. Thesharpener is manufactured in one size only,and is suitable for sharpening mowershaving 10 -in. blades or wider. If yourmower is wider than the sharpener, yousimply put a drop or two of oil on the crossbar and slide the sharpener backwards andforwards across the bar, so as to contact

An efficient automaticdoor control.

the full width of each blade. The sharpenersells at the moderate price of only 28. [119.]

An Automatic Door CloserF you desire your doors to close easilyand quietly you should certainly fit the

automatic door -closing device shown onthis page. Inside the cylinder shown, is aspindle controlled by a spiral spring, whosetension is affected by the revolving of thespindle caused through opening and closingthe door. The tension of the spiral springincreases when the door is open andactuates the door so as to close it. Achecking effect is obtained by the oil in thefluid chamber, which works in conjunctionwith a valve to obtain a cushioning actionin order to retard a too sudden motion, soas to prevent slamming. Should, however,the door be closed with excessive force soas to tend to shut the door more quicklythan the checking means in the apparatusallow, the special resilient portion of thegirder arm is so made that it will yield andprevent any damage or loosening of theworking parts. The device costs 12s. 6d.[120.]

A Four -in -One Kitchen Knife

THE knife shown on this page is bothnovel and handy, and obtains its

cutting edge from an old razor blade. Itcan be made to peel, core, scrape or slicefruit in a short space of time and is perfectlysafe when in use. When the cutting edgebecomes blunt, all you have to do is to fit anew razor blade. It sells at the low price of6d. [121.]

An Ingenious Bench FixtureAUNIQUE and ingenious bench fixturewhich enables articles (either held

direct or in a vice or jig) to be swivelledor tilted to any position and rigidly held in

A four -in -one knife which obtains its cutting blade fromwed razor blades.

that position, is now on the market. It isobtainable in a small or large size, and theswivelling movement is through 360degrees, the lock operating in any position.The canting movement is entirely inde-pendent of the swivelling movement andoperates through 90 degrees. A fixed stopis fitted to prevent further movement.Thus an infinite number of positions ispossible, so that the work, once held, canbe turned to any desired position withoutre -gripping. Where used as a vice mount-ing, if choice of vice is available, it is recom-mended that the lighter types of vice beused, especially in the larger sizes. This isnot only better for the mounting, but isinfinitely better for the operator, as mani-pulation is so much easier and more rapid.The price of the small size is 178. 6d. in greyiron, 228. 6d. in semi -steel, and 278. 6d. inmalleable iron. The price of the larger sizeranges from 32s. 6d. to 523. 6d. [122.]

The Odd -Job Household Repair Outfit

TOOLsets vary tremendously. They

may be nothing more than toys, or theymay be complete enough for a carpenter-intended for people who want to makethings. But neither of these meets the needs

A compact and portab e set of tools that will beappreciated by many handymen.

of an average householder. What he wantsis an outfit adequate to deal with thehundred -and -one little jobs that crop upconstantly in every house. The lost screw,the running tap, the loose terminal, or thebroken picture wire. In fact, what is reallyneeded is not only a small, carefullyselected set of tools, but also a very com-plete assortment of nails, screws, staples,and similar small fittings. Here, then, issomething quite new-something whichevery householder will find of invaluableassistance-The Odd -Job Household RepairOutfit. It has been produced for the manwho, sensibly, attends to minor houserepairs himself. The contents are sufficientfor any little job likely to arise-yet it is ascompact as anyone could wish. One of itsvery big advantages is this : all your toolsare collected together in one handy box.You don't have to chase upstairs for thescrewdriver-downstairs for the hammer.You know where everything is. You'llagree this ingenious little collection fulfilsa long -felt want. It costs 21a. [123.]

ORDER NEXT MONTH'SISSUE NOW!

Many more fascinating articlesand diagrams

A novel and rapid paper trimmer. Simply loosen thewing nut and set the blade to the required width of cut,on the scale provided,each division being }in. It costs4/3



THE

HOBBY

OF

TO -DAYMake your ownmodel aircraft (non -flying) with SKYBIRD

components. SKYBIRD sets of parts are engineer -constructed,accurate in detail, and true -to -scale (1/72). They are of metal, woodand celluloid. There is also a wide range of accessories for planning

and constructing aerodrome schemes, etc.Illustrated above is the Gloster "Gauntlet." The set of constructive parts for this

new model costs 2/6.If you are interested in ships, you can make wonderful scale water -line models (I -in.

to 100 -ft.) from the SHIPSERIES range of components.

POST THIS COUPON TO -DAY

SKYBIRDSSKYBIRDLEAGUE

Messrs. A. J. HOLLADAY & CO. LTD. (Dept. P.M.),3 Aldermanbury Avenue, London, E.C.2.

(a) Please send me full particulars and address of nearest agent.(b) Please also send me latest copy of THE SKYBIRD for

which I enclose 7d. In stamps.Cross out either (a )or (6).

Name

Address

"WILCO " ELECTRIC DRILL

PRICE

42/ -Carriage

Paid.

Will do all the ordinary drilling required in the home or workshop.Capacity V. The high speed motor is geared down to give plenty ofpower. Voltages 200/220 volts or 230/250 volts. A.C. ONLY.

Further details on request if required.L. WILKINSON, 8 City Road, LONDON, E.C.

GRAFTON ELECTRICCOMPANY

AERATORS FOR AQUARIUMS !!Keep a constant flow of air into youraquarium tanks. The aerator illustratedworks from A.C. mains and will run con-tinuously without trouble at infinitesimalcost for current.Adjustable air flow. Overall dimensions,4 inches high x 2i inches dia. PRICECOMPLETE 30/ -

Full details on application.1935 Catalogue 3d. Post Free.

(DEPT. P), 54 GRAFTON STREET,TOTTENHAM COURT ROAD,

LONDON, W.I

PROTECT YOUR SET

Goltone Components are obtainable fromFirst-class Radio Stores. Refuse substi-

tutes-if any difficulty write direct.

FREEON REQUEST

5935 6o -page RADIOCATALOGUE of interestto every radio enthusiast.

rircl3GoldirnNDLE TON .....1V ILM/V401t Si t 11PE0.

AGAINST

"GOLTONE"BAKELITE

LIGHTNINGARRESTER.ROBUST CONSTRUCTION,FITTED IN A FEWMINUTES, PRACTICALLYINDESTRUCTIBLE.Complete with Galvanized

parts, and strongmassive metalIron Bracket,

Bakelite Cowl.1221/476 each

"Goltone" InterferenceSuppressing Devices.

Interference Compensa-tors, Mains H.F. Chokes,High Voltage Condensers,Screened Aerial DownLeads,ImpedanceMatchingDevices, Screened Trans-mission Lines, ScreenedTubings are some of thewide range manufactured.Catalogue and folders withInterference Elimination

facto sent on request.

SLIP A MOVIE CAMERAIN YOUR POCKET . . .Making movies will) addfurther enjoyment to yourEaster holiday. You'llfind it a simple yet thrill-ing pastime, and anyadvice you need we willgladly give you.

CINE "KODAK" 8(as illustrated)

HALVES running COSTSWith fixed -focus f/3.5 lens,exposure guide, footage indi-cator, and eye -level finders.

29 . 17 . 6Nine monthly payments of 23/1.

PATH ESCOPE " B "Simple to use, with strong clock-work motor drive. Strongly con-structed, attractively finished,fitted with high-grade Pathef/3.5 anastigmat lens. £6.6.0Nine monthly payments of 14/9.

"DEKKO "CAMERAThree speeds, half, normal,slow. Can be used for snap-shots, time exposures, singleand animated. With Dallmeyerf/3.5 lens. £6. 6 . 0Nine monthly payments of 14/9.

FIRST EASY PAYMENT

SECURES ANY MODELPay balance while you are enjoy-ing its use. Surely you can't affordto miss movie -making when acine camera is brought withinsuch easy reach? We pay goodallowance on your used camerain part exchange.

CITY SALE & EXCHANGE(1929) LTD.

59 & 60 CHEAPSIDE, LONDON, E.C.2



Generously Illustrated ==

Constantly brought up to date

NEWNES

Home Mechanic SeriesHANDYMAN'S ENQUIRE WITHIN

Contains hundreds of practical ideasand hints, which have been provedafter years of use. An invaluable

book for the home handyman.

MOTOR CAR UPKEEP AND OVERHAULAdjustment and repair of motor carssimplified for the owner -driver. Thisbook supplements the instruction

book supplied with a car.

ACCUMULATORSCharging, maintenance and care ofaccumulators clearly explained. Bythe editor of " Practical Wireless."Of value both to the car owner and

the wireless enthusiast.

TOY MAKING FOR AMATEURSComplete directions for those whowish to take up the fascinating hobbyof toy making from inexpensive

materials.

THE HOME WOODWORKERHow to make useful householdarticles such as a writing desk,kitchen table, step ladder, pictureframes, etc., with the simplest tools.

SIMPLE ELECTRICAL APPARATUSAn elementary guide for the amateurscientist, giving details of variousapparatus which can be constructedwithout great skill and at slight

expense.

MODEL BOAT BUILDINGAll types-sail and mechanicallypropelled. Every model shown hasbeen constructed, tested and found

to give full satisfaction

25 SIMPLE WORKING MODELSIn making these, only the mostordinary tools are needed, and intheir construction (as in that of allother articles described in this series)

no lathe -work is necessary.

MODEL AEROPLANES & AIRSHIPSExperimental and practical modelsof all types with full instructions asto the best materials to use and thebest procedure in construction.

Price V. net

All the hand -books of this very popular series are written by experts andprofusely illustrated. They can be obtained price 11- each at all

Bookshops, Newsagents, etc.

GEORGE NEWNES LTD., 8-11 Southampton St., Strand, London, W.C.

sfr:Trrense cry



A Midget Water SoftenerTHE neat water softener shown on this

page consists of a white porcelaincylinder, 7 in. high and 3} in. in

diameter fitted with non -tarnishable fit-tings. Simply fit the rubber hose to anytap as shown-either hot or cold-gentlyturn on the tap and you instantlyhavelperfectly soft water. The

- 3 "-

A midget water softener that can be fitted to a tap in afew seconds.

device does not leak or drip, and is just aseasily removed. A testing set is suppliedfree with the apparatus, and by adding a fewdrops of the special soap solution supplied,to the water and shaking it in a bottle, youcan instantly tell whether you are receivinghard or soft water. Soft water will turnthe solution into a creamy lather, but ifthe water is hard it will become cloudy withscum and there will be little or no lather.The water softener costs 25$., but a specialnon -tarnishable wall bracket, completewith screws and wall plugs, is supplied,if desired, at an extra cost of 5s. [110.]

A Set of Handy Measuring SpoonsTHE spoons shown in the illustration on

this page are graded in size from tea-spoon to 1 tablespoon, and will be founduseful for a variety of purposes. They aremade in aluminium, and may be obtainedfor 18. post free. [111.]

Interference Compensators for WirelessTHE certain way of curing interference

is at the source. There are extremecases when it is impossible to entirelyremove the trouble, but it can be reducedto a minimum by using an interferencecompensator now being made by a well-known wireless firm. Sparking caused bycontacts being broken causes noises to beradiated through the mains. It is thepurpose of the interference compensatorto block this radiation. To a large extent,

deners. Each mould makes a tile 14 in.long and 7 in. deep, and by means of aninset supplied, three tiles 4i in. long canbe made in one mould, for curves. All youhave to do is to mix the cement and pourit into the mould. These moulds alsoenable you to make crazy paving, as canbe seen from the accompanying sketch.A set of six moulds to make 7 ft. of edgingat a time costs 1 ls. 6d., or a half set can beobtained for 6s. A set of interlockingmetal strips for making crazy paving costs

..--FILAMENT BURNER

An ingenious electr'c gas lighter.

12s. 6d., or a half set is obtainable for68. 6d. [114.]

A Speedometer for Pedal BicyclesA DEVICE which will certainly prove of"particular interest to cyclists is amoderately priced speedometer, which canbe attached to the handlebars of a bicycleby means of a clip and link. The drivingsprocket supplied is attached to the spokesof the wheel by means of screws and spoke -nuts. If, however, it is found necessaryto fit one of the spoke -nuts on to the lowerspoke, a brass spacing collar, which isprovided, should be used to prevent dis-tortion of the driving sprocket. Thespeedometer is provided with a standardflexible shaft, 24 in. long, for machineswith 26 -in. wheels, and 29 in. long for28 -in. wheels. When fitting the device,care should be taken to obtain the correctmeshing of the fibre pinion at the foot ofthe cable, with the driving sprocket, andalso when connecting the top end of theinner flexible cable to the instrument. Thebracket for supporting the bracket at thepinion end should be fitted to the hubspindle. The speedometer will registercorrectly whether fitted to the right or leftside of the machine. It costs 12s. 6d.complete. [115.]

vrrrrrrn.

The address of the makers ofany device described belowwill be sent on applicationto the Editor, PRACTICALMECHANICS 8-11, Southamp-ton St., Strand, W.C. 2.

Quote number at endof paragraph.

the noises arise from H.F. currents, theircharacteristic sign being normally a con-tinuous crackling or rustling, while L.F.currents are apparent by a hummingsound. By connecting compensators atthe source, these interfering currents areshort-circuited and rendered ineffective,thus preventing radiation. The inter-ference compensator costs 9s. 6d. [112.]

An Electric Gas LighterWE show on this page an electric gas

lighter which is of simple constructionand is entirely foolproof. As can be seen,it is worked off an ordinary dry battery,which is capable of lighting your gas some7,000 times. It is safe, and there is nodanger of sparks ; just press the button andthe gas is ignited. The ring shown in thesketch near the switch enables the gas -lighter to be hungwhere most con-venient for use. Itis certainly economi-

A set of measuring spoons that will be found useful fora variety of purposes.

cal, and costs 5.e. complete. Dry batteryrefills cost 2s., and spare burners ls. 3d.each. [113.]

Novel Edging MouldsTHE moulds shown on this page are

both ingenious and novel, and theyshould certainly prove popular with gar -

Details of the moulds for making garden edging and crazy paving.



Surface PlateACAST-IRON plate resting on three feet,

and having an upper surface scrapedperfectly true. It is

strengthened on the under-side by ribs, the arrangementand size of which are care-fully calculated to ensure theplate remaining true undervarying conditions. A sur-face plate is used for testingthe accuracy of the sliding sur-faces of small machine partswhere a true sliding contact isessential, such as lathe slide -rest parts, or the slide -valveof an engine cylinder. Seealso Scribing Block or Sur-face Gauge (Fig. 20).Taps

Used for cutting internalthreads. Taps are made of cast steel, andhave three or four grooves, or flutes, cutat equi-distant points round the tap form-ing cutting edges. For cutting threads inthe larger sizes, it is the usual practice to

employ three taps,viz., taper, the second,and the plug tap. Thetaper tap has itsthreaded end turnedto a gradual taper, sothat the end of thetap can easily enterthe hole when starting/// the thread. The" second " tap is onlyslightly tapered at theentering end, the re-maining threads beingof the full diameter.The plug tap, which isused last for takingthe finishing cut, hasall its threads of thefull diameter.

For gripping a tap/, when in use a tap

wrench is employed.One pattern has an ad-justable jaw arrangedto grip the squaredends of taps of differentsizes. There is a handleat each end, one ofwhich acts as an ad-justing screw for themovable jaw. An-other pattern of smallercapacity has theclamping screwthreaded through one

of the handles, the end of the screw beingknurled. A hole is made in the knurled endto take a tommy bar for tightening up theend of the screw against the squared endof a tap or any other small tool within itscapacity.

Fig. 20.-A scribingblock which is used formarking the surface of amachine part, or casting,or for locating theposition of holes to bedrilled, and other

purposes.

Fig. 24.-Vice dams are pieces of sheet metal, usuallylead, bent to fit over the jaws of a vice.

Fig. 23.-A smallbench vice which isused for holding work firmly wh le beingdrilled and filed.

AN A.B.C. OF

ENGINEERING

TOOLS(Concluded from page 285, March, 1935, issue)

Tinmen's ShearsTool used for cutting thin sheet metal

and wire. The long handles, in proportionto the length of the blades, enable a goodcutting pressure to be applied (Fig. 22).

Twist DrillA drill made of cast steel,

and formed with a spiralflute which enablesthe metal shavingsto easily get freewhen a hole is beingdrilled. Twist drillsare made in varyingdiameters from 1/32in. upwards, the :smallersizes having round shanks.The larger sizes are alsoobtainable with Morse taper

A STANDARD WORKNEWNES ENCYCLOPAEDIA OF

POPULAR MECHANICS

by F. J. Camm. 5/- or 5/6 by post fromGeo. Newnes Ltd., 8/11 Southampton

Street, Strand, London, W.C.2.

shanks or square taper shanks,the latter pattern being intendedfor use with a ratchet brace(which see).

Vernier-See Caliper Gauge.

ViceUsed for holding work firmly

while being drilled or filed. Thereare many patterns of vicessuitable either for lightor heavy work. A vicein common use is the benchvice, which is providedwith side lugs for screwing

it on to the bench. Made in varioussizes, these vices have steel jaws rangingin widths from 2} to 6 in. For lightmechanical work a table vice is very useful.There are several patterns, one of which isshown in Fig. 23. A screw clamp is pro-vided for holding it firmly on the bench ortable, and there is also a small steel anvil,just behind the rear jaw, on which lighthammering or riveting can be done. Somebench vices are fitted with an " instant-aneous -grip " device operated by a trigger,which when pressed allows the movable jawof the vice to slide freely in and out. Thework is placed between the jaws in theordinary way, the movable jaw is thenpushed up against it, and the handle givenhalf a turn which holds the work firmly inplace. For holding small metal parts, andscrews, for light filing and other purposes,a hand vice is used, the jaws being closedby screwing up a wing nut. For holdingpipes, tubes and rods for cutting or screwthreading, a tube vice is employed. Thistool is largely used by gas -fitters, and canbe bolted on to a bench or hand -cart. TheV-shaped jaws, the upper one of which hasa number of teeth on its gripping surface,hold the tube or rod firmly and prevent itfrom turning when screwing tackle is beingused.

Fig. 21.-A surface plate, which consists of a cast-ironplate resting on three feet, and having an upper

surface scraped perfectly true.

Vice ClamsPieces of sheet metal, usually lead, bent

to fit over the jaws of a vice to preventfinished work being scratched or marked bythe teeth of the jaws (Fig. 24).

Fig. 22.-Tinmen's shears. A tool for cutting thin -sheet metal and wire.


A Handy Pair of Tongs

THESE handy wire tongs will be foundvery useful for recovering small objects,

such as nuts, etc., from cramped places inwireless sets.

Two pieces of springy wire are shiped, asin the illustrations. To pick up an object,slide the shorter wire down on the thugs;the ends come together, grasping theobject. This tool is easily worked with onehand.

TO GRASP AN OBJECTSHORTER PIECE OF WIREIS SUD DOWN

PRONGS TURNEDIN SLIGHTLY

Details of the tongs for recovering objects from awkwardplaces.

Splitting MicaA /HEN making fixed condensers it is

often desirable to split up the micasheet, as purchased, into much thinnersheets. By using the thinner sheets, notonly is the capacity of the condenserincreased, or, inversely, a fewer number ofsheets required, but the complete con-denser is, of course, very much cheaper.Mica is easily split with a knife, but somedifficulty may be experienced in gettingall the separated sheets of the same thick-ness unless some device is used for gauging

64,00,140OFFf-ACA'..£411,8ZADE

- A simple method of splitting mica sheets.

NEWNES PRACTICAL MECHANICS

THAT HINT OF YOURSEvery reader of PRACTICAL MECHANICS must

have originated some little dodge which would be ofiterest to other readers. Why not pass it on to ns ?

For every item published on this page, we will pay 5s.Address your envelope to "Hint," PRACTICALMECHANICS, George Newues Ltd., 8-11SouthamptonStreet, W.C. Put your name and address on everyitem. Please note that every hint sent in must be

original No other correspondence what-'', ever should be included.

them. An easy way of doing this is shownin the sketch. The blade is a piece of hack-saw blade ground off on one side to a knifeedge, and drilled through (it will be neces-sary to soften the ends of the blade to dothis) so that it can be fixed to a piece ofhard flat wood with two wood screws.The blade is packed away from the woodwith pieces of paper, the thickness of thepaper deciding the thickness of the splitmica sheet. As a guide, the thickness ofan inside page of PRACTICAL MECHANICS isabout -003 in., and an outside cover.005 in. The corner of a piece of thick micais pressed against the edge of the blade andpushed through, by pressing the fingers ontop, the lower piece emerging from theunderside of the knife of the correctthickness.

Another Use for a Compass

rlAN ordinary draughtsman's compasscan quickly be converted into a tool

for cutting circular holes in pieces of paper,card, etc., should the occasion arise.

How a compasscan be used forcutting circular

holes.

Take an ordinary razor blade and placeit between the blades of the compass penat an angle, so that only, one corner of bladeis touching the material you intend to cut(as in sketch).

To prevent the blade slipping, place twopieces of card, one on either side of bladewhere the points come in contact with theblade, then tighten.

A Simple Frame AerialI FOUND that by using an aerial of theI type shown in the accompanying sketch,and connecting it to the grid of the firstvalve direct, it enabled me to use a simpledet.-2 L.F. set in any room as a portableset. To vary the amount of " capacity "to earth, and thereby control selectivity, Iplaced the aerial either on the floor or on achair.

Soldering without Gas or Electricity

WHERE electricity or gas is not avail-able this soldering stand and heater will

be found very useful. Obtain a tin, onewhich does not leak, and solder wire sup-ports to the tin, which are then bent into

olDI

AncwoREO.6:161/wwivG OF G"Pinzwy6

(LEFT FREE)

72rRni

ENDO,10/romu

337

Tuery gawp20X/6"

A handy and efficient frame aerial can be made asshown.

position, as shown in the sketch. Nowobtain a piece of f -in. copper tubing andpush it through a hole in a cork or stopper,which projects about 2 in. into the tin.Push through enough wick so as to nearlyreach the bottom of the can, and then fillwith methylated spirit.

Earthing to a Water Tap

THE following idea may prove of use toreaders interested in wireless, for a good

earth connection to a water tap. Afterturning off the water, unscrew the top partof the tap. Now from a piece of thin brass,cut out a washer to fit over the thread ofthe tap. Firmly solder your earth wire tothe washer by means of the holes drilled inthe tag and rescrew the tap. This will provemuch better than a clip.

CORK ORWOODENSTOPPER

WIRE SUPPORTSSOLDERED TOCAN.

A useful soldering iron stand and /mato.



isil_NT76c,

APPAPATUCttpligemsFOR STUDENTS' LABORATORIES

Complete range of CHEMICALS in Bottles from 3d. each.-Extensive selection of APPARATUS, including Beakers.Flasks, Graduated Ware. Condensers, Retorts, Balances, etc.SPECIAL PARCEL OF APPARATUS.I Flask, flat bottom 150 c.c., 1 Beaker, spouted 100 c.c., 3 TestTubes a in. x 3 in., 1 Thistle Funnel 20 cm., 3Glass Tubing, 1 Rubber Cork 2 holes, 4 inches Rulsber Connection Tubing, 1 Glass Stirring Rod. Free

(Scientific Dept. A.) 60 HIGH STREET,STOKE NEWINGTON, LONDON, N.I6

Write for Catalogue-FREE.BECK

BE A MANI positively GUARANTEE to giveyou Robust Health, DoubledStrength and 10-25" snore musclein 30 days or return your moneyin full. The famous STEBBINS4-Ln-1 Course consists of fourgreat coursesin one.yet costs only5/- at free. It has been proved0:: The most effective HEALTHand EIS ERGY System ever de-vised; IV It quickly builds NOR-MAL WEIGHT and VIRILEM 4N HOOD; (3) It develops aStrong Will, rigid SE LF.CON-TKO I.; and (4) It includes anamazing SUCCESS and PER-SONAL MAGNETISM Course.

Complete Course. 5/ -No extras, no appliances to

Pupil S. Davey (London) purchase.Further &Mile sent privately, under plain, sealed cover.LIONEL STEBBING, STEBBING INSTITUTE,

Dept. O.P., 28 Dean Road, London, E.W.2.

DON'T BE BULLIEDLearn to fear no man. TheBEST self-defence ever in-vented, namely, JUJITSU.Easy to learn. Send 2 pennystamps for SPLENDID ILLUS-TRATED LESSONS, PhotoAETICLE, Testimonials andparticulars, or P.O. 1/- forFIRST PART of my course.You will be more thandelighted.Dept. P.. Blenheim House,Bed-f ont Lane, Peltham,Muldlesex.

(ic3LIGHT AND RAY CELLS.-Selenium Raycraft,21/-; Kingston. M.. Raycraft outfit with relayand amplifier, 42/.. Photo -Cells R.C.A. andB.T.P., for sound on Film, Television and RayWork, 15/- and 25/-. Beck Angle Prisms mountedin carrier, 6/6. Micrometer adjusters for lens, 1/..Eyepieces with prism and I lenses for photo-cell inspection, 12/6. New Ever Ready ServiceInspector's Headlamps with Battery Holder, 7/6.

TELESCOPES.-Naval Gun -Sighting Telescopes, internalfocus ring. 24 in. long, 2 in. dia., weight 6 lb., magnification 6,for short and long range. Cost 615. Sale, 17/4. SpottingTelescopes, 17 in. 0 If in., by Watson, 25/-. 120 lb. PressureGauges, 2/6.MOTORS.-Special line of A.C. fractional H.P., 100 volt.15/-; 220 volt, 17/6. Large stock of all sizes for Cine work.State volts and supply.

Write for Sfrecial Bargain List " P.M." Free.ELECTRADIX RADIOS

219 Upper Thames Street, London, E.C.4TelePhone: Central 4611.

ELECTRADIX BARGAINS

WHY BE THIN ?DON'T BE AFRAID TO STRIPENJOY THE SUMMER SUNSHINE

Thousands have put on weight and muscular tissue withthe aid of

VITAEPON CHAiltrilarsinA customer writes gained 18 lbs. of solid flesh insix weeks and am bubbling over with energy."Vitaepon is not a drug-simply take two tablets

with the morning and evening meal.Obtainable only from :-

WESTCOTT & CO. (Dept. P.),37 Albemarle Street, Piccadilly, London, W.I.

For Week's Trial Supply send P.O. for 3/-, or I5/ -forfull six weeks' course. Abroad by registered post, 3/6

and 16/-. post free. Sent in plain covets.A new book by Medical Expert. "Thinness: Its Cause

and Cure,' sent free with every six weeks' course.

USES FOR WATER -GLASSThousands of tons of Water -Glass are sold annuallyfor trades varying from oil -refining to paper -making

THE modern chemist specialises infinding new uses for old materials.With none has he had greater success

than with water -glass. A hundred usescould be quoted for this material, andthousands of tons of it are sold annuallyfor trades which vary from oil -refining topaper -making ; for the potters' trade to thebuilders', from gold -mining to bottle -washing, so that it is superfluous to mentionthat the same material is used in egg -preserving.

Water -glass possesses a remarkable affi-nity for oil and grease. The manufacturerof lubricating oils uses water -glass toseparate those last traces of paraffin waxwhich could do so much harm if they stayedin the oil and carbonised on hot bearings.The oil man at the well -head, when facedwith a heavy " crude " which contains toomuch wax and bitumen, separates the oilwith water -glass in the same way so thathe can pump it along his pipe -lines. Thereare firms which do a thriving business inrecovering oil from machine swabs andcotton waste, again by using a water -glasssolution.

A " Detergent "Breweries and dairy companies use water -

glass in solving the problem of immensedaily "wash-ups " of thousands of milkand beer bottles. Chemists who haveraised the business of washing-up to thescience of " detergency " find that a solu-tion of water -glass spreads over dirtysurfaces and cleans away dirt and grease ina remarkable manner. A solution of 1 oz.in a gallon of water will be found to be mosteffective as a cleaning solution in the work-shop.

It is most unique, because it is the onlyalkaline washing material which does notharm aluminium. It is well known thatwashing soda corrodes the surface ofaluminium. To illustrate this difference,you have only to boil a piece of aluminiumwith soda. Hydrogen is generated fromthe surface of the aluminium in a cloud ofbubbles, which immediately disappears ifa drop of water -glass is added. Thisproperty is not only used in washing thelarge aluminium vats which are common inindustry ; it also enables shaving creamsand tooth -pastes to be packed in aluminiumtubes. These materials are faintly but

" Oil -break" off a wire gauzein water -glass solution.

Oi. will not break off the gauzein a soda solution.

sufficiently alkaline to attack and destroytheir containers. They are rendered in-nocuous by the addition of a trace of water -glass to the pack.

An AdhesiveIf water -glass is dried it sets with rock-

like firmness. It is thus used as a rapid -setting adhesive in making mill -board. Amill -board -making machine is exacting inits demands. It takes thin sheets of paper,sticks them together and rolls up thefinished cardboard at the rate of 300 ft.per minute. The bond between the layers

A silica garden made by pouring a water -glass solutioninto a tumbler and then introducing crystals of copper

sulphate, iron sulphate, etc.

of paper has to be made and set in the spaceof a few seconds. A carefully made-upwater -glass solution is the only adhesivewhich stands up to this service. It gives aninstantaneous bond which is stronger thanthe fibre of the paper itself.

A De-FlocculantWater -glass has the property of making

clays plastic and fluid. It deflocculatesthem, and so another wide range of uses is

opened up. The paper.maker uses it to thin thefilling clays he uses tosurface writing and print-ing papers, so that theclay will flow smoothlyto the paper -makingmachines and will stillhave plenty of body. Inmining the same clay inthe Cornish china -claypits, water -glass is usedto float off the clay fromthe grit of mica andquartz. A similar use isin the cleaning of goldand zinc, copper and tinores from rocky gangue.The potter finds thatwater -glass makes hispotting -clays mould moreeasily.



A Water -Glass PaintThen water -glass is used in the final

glazing and decoration of crockery. It isthe base of many distempers and water-paints. A simple fire- and water -proofpaint for colouring electric light bulbs andglassware can easily be made as follows :-

A solution of 1 part of water -glass in6 parts of water is made up. A secondsolution of sulphate of ammonia is made upto full strength, as much as will dissolve.The two solutions are mixed to form thebase of the paint. Into the base, any fire-proof colouring material, such as jewellers'rouge, ultramarine blue, brilliant green orchrome yellow is mixed to give a thin slurry.The surface to be painted is washed withwater -glass and the paint is applied andallowed to dry. It is then " fired " byputting it in an oven at 300° F.-ap ordinarygas -oven at full heat is just about right.The colour sets firmly, or if the colouringmatter is omitted the base sets with a whitefrosted finish.

A Silica GardenNo account of the uses of water -glass

would be complete without describing thefascinating experiment known as the

" Silica Garden.' A 1 in 6 water -glasssolution is made up and poured into atumbler. Into this crystals are dropped ofsuch substances as copper sulphate, iron

The glassware on the left is washed with water -glass,and on the right with washing soda. It will be seen

that water -glass runs off cleanly.

sulphate, cobalt and nickel nitrates, evenordinary Epsom salts. Overnight thecrystals begin to sprout and daily grow upinto coloured stalagmites, which eventuallyfill the glass with feathery spires.

THE THOMAS GRAYMEMORIAL TRUST

Prizes offered in 1935 for the Improvement and Encouragementof Navigation

NDER the will of the late Thomas L.Gray, the Royal Society of Arts hasbeen appointed residuary legatee of

his estate for the purpose of founding amemorial to his father, the late ThomasGray, C.B., who was for many yearsAssistant Secretary to the Board of Trade(Marine Department).

The objects of the Trust are " The ad-vancement of the Science of Navigationand the Scientific and Educational interestsof the British Mercantile Marine."

The Council now offer the followingprizes :-Prize for an Invention

A prize of £100 to any person who maybring to their notice an invention, publica-tion, diagram, etc., which, in the opinionof the judges appointed by the Council,is considered to be an advancement in theScience or Practice of Navigation, pro-posed or invented by himself in the periodJanuary 1st, 1930, to December 31st,1935. Entries which have already beenconsidered by the judges in the years1930-34 are not eligible for further con-sideration unless they have since beenmaterially modified.

In the event of more than one suchimprovement being approved, the Councilreserve the right of dividing the amountinto two or more prizes at their discretion.Competitors must forward their proofs ofclaim on or before December 31st, 1935,to the Secretary, Royal Society of Arts,John Street, Adelphi, London, W.C.2.Prize for an Essay

A prize of £100 for an essay on thefollowing subject : " Modern NavigationalAppliances."

(1) Appliances made possible by elec-tricity on board, e.g., Wireless D.F., EchoSounding, Gyroscope, etc.

(2) Appliances not depending on elec-tricity, e.g., Range Finding, SoundingMachine, Compass, etc.

Candidates are expected to deal withboth sections. They should write from apractical point of view and give their viewson the advantages and disadvantages orfailures (if any) of modern electrical aids tonavigation, based if possible on personalexperience.

Competitors must send in their essaysnot later than December 31st, 1935, to theSecretary, Royal Society of Arts, at theabove address.

The essays must be typed in English.They must be sent in under a motto,accompanied by a sealed envelope enclosingthe author's name, which must on noaccount be written on the essay. A breachof this regulation will result in disqualifica-tion.

Both competitions are open to personsof any nationality, but, in the case of theEssay Competition only, competitors mustbe past or present members of the seafaringprofession.

The judges will be appointed by theCouncil.

The Council reserve the right of with-holding a prize or of awarding a smallerprize or prizes, if in the opinion of thejudges no suitable invention or essay issubmitted.

The Council also reserve an option on thecopyright of the successful essay or essays,but do not claim any rights in respect ofany invention to which a prize may beawarded,

Things are happening to -daywhich vitally affect you!

If you are about 18, perhaps you aregetting settled in your chosen work andalready feeling the strain of competition fora better position. If you are in the 40's,your family responsibilities are near thepeak, the necessity for money is tense-and younger men are challenging your job.And men of the ages between 18 and 45 facesimilar problems, in one form or another.

The most valuable employment securityto -day is the security a man creates forhimself-in himself ! Through training, heis able to adapt himself to new conditions,to utilise experience without being handi-capped by habit ! He masters jobs andmakes new jobs. He meets emergencies-and is not overwhelmed by them. Andthis is an age of emergencies.

For 44 years the International Cor-respondence Schools have helped thoughtfuland ambitious men to acquire the trainingthey need. To -day, with this need moreurgent than ever, this world-famous institu-tion oilers greater opportunities than ever.Why not permit us to show you the way togreater security and larger earnings ? Ourexpert advice is free. Write to -day.

...COUPON FOR FREE BOOKLET...

INTERNATIONAL CORRESPONDENCE SCHOOLS,LTD.,

Dept. 95, International Buildings, Kingsway,London, W.C.2

Please send me your booklet containingfull particulars of the Course of Correspond-ence Training before which I have markedX. I assume no obligation.

CAccountancyO AdvertisingCAeronautical EngineeringCArchitecture['BookkeepingEBuildingCChemical Engineering

Engineering['DraughtsmanshipOElectrical Engineering Engineering Design

DExaminations, state which

['Marine EngineeringEMechanital Engineering0Mining EngineeringnMotor Engineering['PlumbingCRadioERailway Equipment and

RunningCSalesmanshipOSteam EngineeringOTextiles['Woodworking

The I.C.S. teach wherever the post reaches, and havea wide variety of courses of Study. If, therefore, yoursubject is not in the above list, write it here.

Name

Address



SMOKELESS

AND

ENJOYIT MORE

An easy, simple way to cutdown your smoking.

Save money, safeguardyour health, and enjoyyour smoking MORE. Sucka " SAVA-SMOKE," whichcontains neither drugs notchemicals. These littletablets definitely controlyour smoking, and, by re-freshing the palate, givemore smoke -joy f r omfewer cigarettes. A C TNOW. Write for full de-tails free OR forward aP.O. for a Ss. ad. Box. Postfree.

SAVA- SMOKE(Dept 131), 131 REGENT STREET, LONDON, W.1.

USEFUL-INSTRUCTIVE-ENTERTAINING-Over a Hundred uses

*Microphone*Detectorphone

to 1 /-Postage 2d. '4Everyone fully(ia

*Baby Alarm, etc.Reduced from 3/6

tested andguaranteed

The SCIENTIFIC SUPPLY STORES (WIRELESS) LTD.Dept." M," 126 Newington Causeway, Elephant & CastleLONDON, S.E. 1. Phone : HOP. 4177

"THEWONDER:

OF THEMICROPHONE."

A comprehensivebook containingover 25 diagrams

and illustrationsshowing actualcircuits andexperiments.

A source of end -I ess educationand amusement.

D. PostPrice la free.

HUMATAGRAPH(Hygrometer)

Indicates the humidity of theair with scientific accuracy.Models for the home and indus-trial purposes. Matt Black,25/- ; Chromium plated, 28/-.Pocket model in case, 14/6.

C. L. BURDICK MFG. CO.90-44 HOLBORN VIADUCT

LONDON, E C.1.

Sold in 6d. and I,- tins at all CycleAccessory Dealers, Tool Shops,

Ironmongers, etc.Write for yourfres copy "Joining of Metes" to

SW BURN ETT&GREAT WEST ROAD, L.r,vozT;','

C,PXONE: MOUNSLOW 0476

apivimariGOOD IDEAS-

are often rejected because of uncon-vincing drawings!Let us prepare attractive illustrationswhich will convey your idea quickly andclearly to Manufacturers, Editors,Agents, etc.We specialise in Patent Office and Techni-

cal drawings of all descriptions.Write or 'phone us at

HIGH HOLBORN HOUSE,HIGH HOLBORN, W.0.1.

Hoc. KU

PECULIARITIES OFSPINNING BODIES

AY body, when spinning or ,.rotating,possesses certain marked peculiaritieswhich are entirely absent when it is

at rest.For one thing it acquires an extra-

ordinary rigidity.Obtain a disc of quite thin paper and

Fig. 1.-The chain held in the drill chuck ready foscanning.

Fig. 2.-The second operation showing the chaincommencing to spin.

fix its centre so that it can be rotatedrapidly. When spinning, it resists, in avery marked manner, the blow of a stickor even of your fist, as if it were a disc ofsteel. Its flexibility has entirely dis-appeared.

The Rigidity of Smoke Rings,__Many readers have no doubt experi-mented with smoke rings and noted theirpeculiar rigidity whilst travelling throughthe air. See what happens, however, whenyou try and cut it in two with a knife.

It will be found that if a body is sup-ported below its centre of gravity it hasone axis (the longer) about which it prefersto spin-but when supported above itscentre of gravity it prefers another axis(the shorter). Now every body has three

Fig. 3.-The chain at the height of its spin.

principal axes, and according to circum-stances there is always one axis about whichit prefers to spin.

The Spinning ChainObtain a flexible chain, and support it

from above by means of a piece of stringheld in the chuck of a small hand drill(see Figs. 1, 2 and 3). Upon turning thedrill, the chain will open itself in the formof an oval, gradually rising and finallyspinning quite steadily as shown in Fig. 3.A high rate of spin is not necessary, becauseif the spin is too great, the motion maybecome unstable.

A STANDARD WORK..

Newnes Encyclopaedia of PopularMechanics, by F. J. Cam m. 5/- or 5/6by post from Geo. Newnes Ltd., 8/11

Southampton Street, Strand, W.C.2.



MODERN ARCH ITECTUREA multitude of mechanical appliances, water services, plumbing and ventilationare incorporated in a new Sanatorium which has recently been designed by

Mr. W. T. Brown, B.A.

AN interesting and original design fora sanatorium has been completed byMr. William Tatton Brown, B.A., of

6 Bedford Square, W.C.1, in which thedemands of hygiene and economy of upkeephave been combined with a pleasingexterior.

The multitude of mechanical appliances,water services, plumbing and ventilation

set up by the machine. There is also alead -covered table and sink.

On the floor above, an X-ray room isinstalled, the walls and doors of which arelined with lead in order to prevent thedangerous rays from penetrating beyond.

On the other side of the corridor is thesanitary accommodation for the staff of thesanatorium. The " one pipe system " has

The service departments of the Sanatorium show many uses of lead both on the exterior and interior.

systems required for the sanatorium ofto -day have been assembled to form anintegral part of the design.

On the first floor, overlooking a lake, is aseries of private wards, in which privacy hasbeen maintained, even with balconies. Thearchitect has taken advantage of these torelieve the rigidity of the design. At theeast end of the block is an entrance andaccess tower which give a strong verticalaccent to the composition.

Demonstration to the Building Industry ofthe Uses of Lead

The plans were called for by the LeadSheet and Pipe Development Council todemonstrate the uses of various forms oflead in the building industries, and manyapplications-familiar and unfamiliar-areexemplified in the building.

This metal has been used decoratively aswell as functionally in the rain -water headsand down pipes, and also on the mouldedcanopy to the main entrance. On the firstfloor each sanitary unit of the private wardsis equipped with tellurium lead soil andvent pipes, waste and anti-syphonage pipes ;and the supply services and shower -liningare also in lead. An electric cable sheathedwith British non-ferrous ternary alloy iscarried across from the lake to the machineroom in the farther wing, where it operatesa heavy mechanical installation mountedon a lead mattress, which effectively insu-lates the rest of the building from vibrations

been installed, and all the plumbing is inB.N.F. ternary alloy and lead.

Roofing Difficulties CounteredIt has been impossible previously to use

lead for a flat roof intended for promenade,owing to the necessity for the constructionof rolls at frequent intervals. This thearchitect has ingeniously overcome bylaying Solchek tiles between the rolls,providing at the same time a flush walkingsurface and efficient heat insulating for thebuilding and protection for the lead. Onthe north side roof, tellurium sheet leadhas been stuck to the roofing surface withbitumen emulsion, and the rolls and guttershave been concealed with flower boxes.

A FASCINATING NEW HANDBOOK!

POWER -DRIVENMODEL AIRCRAFT

By F. J. CAMM.

96 Pages. 130 Illustrations.

1/- or 1/2 by post from

GEORGE NEWNES LTD.,8-11 Southampton Street, Strand, London,

W.C.2.

5/- 'UNIQUE' SLIDE RULES 3/6BRITISH MADE

llllllllllllllllllllllllllllllllllllllllllllllllllllllll

llllllllllllllllllllllllllllllllll III11111111111111111111111111111111111911111111811111111111

11111111111111111111 11111111111111 111111111111111111111

1 lllllllll 1111111111111111111111E111111E1 mineminig

rulitaaini lulthir'AtirgitiworthivIiuunh

Ten -inch Slide Rule in polished mahogany, celluloid faced withlog -log scale in addition to Scales A. B, C and D. Flexible back.Aluminium framed, view -free unbreakable cursor. Size of rule13 ins. x M ins. Well made and accurate. Supplied with caseand full instructions, including Conversion Tables for MoneyCalculations. Price IV- each (Postage 3d., 3 post free). 6 -inchmodel 316 (Postage 2d.).FREE GIFT of a set of 12 -in. Draughtsmen's Scales, with each10 -inch rule purchased during current month.3i6 The TECHNICAL SUPPLY CO. (P), ci.

Norfolk House, Carden Ave., Withdean, Brighton

EngincersiGuideBright Prospects andBig Pay Opportunitiesfor the trained manWrite to -day for this great Guide whichcontains world's widest choice of home -study engineering courses, and showshow to obtain a Recognised Qualifica-tion such as A.M.I.Mech.E.,A.M.I E. E., A.F.R.A.e.S., etc.Mention branch, post or quali-fication that interests you, toTHE TECHNOLOGICAL/INSTI-TUTE OF GREAT BRITAIN,123 Temple Bar House,

/IILondon, E.C.4. (Founded 1917,19,000 Successes.)

TO Success "'PA "

a watch MaioW11TERPROOF!.1

11

UNBREMtABLEGUARANTEED7 YEARS

against breakages

YOURS 5FOR DON

You can now own a watchworld famous for its relia-bility under the most severeclimatic conditions.

Waterproof-it can evenbe worn whilst bathing IUnbreakable-it can bedropped without fear ofdamage.

Incorporating a patentedfloating non-magnetic jewelledlever movement, shock, vi.bration, dust and sand proof.Time tested under water,chromium patent gland case,24 hour dial. Leather strap.Cash price 59/6 (luminous dial2/0 extra), or yours for 5/. down.

THE GENUINE

made by the. Suppliers to WATCHIMPERIAL AIRWAYS, etc.

TOUR OLD WATCH TAKEN IN PART EXCHANGE.Other models from 25I-.

Write for FREE illustrated catalogue of watches from 6/'down or send your order to -day to:-

G. & M. LANE & CO. LTD.Dept. P.M.E5,

24/26 Ludgate Hill, London, E.C.4



Fully illustrated with constructional details foe build-ing Battery and Maine S.W. Receivers -6v. 8.W Super -het with A.V.C.-All Wave Wavemeser-5-metre Re-ceiver-Simple 5 -metre Trensmitter-Crossfeeder AerialSystem - Battery and Mains S. W. Converters -Amateur Bands Receiver -100 watt Transmitter -Eliminators, etc. COMPELt D BY THE LEADING SHORTWAVE SPECIALISTS. Obtainable from your radiodealer, W. H Smith, or in case of difficulty,STRATTON & Co., LTD (Dept 25), Broms- PRICEgrove Street, Birmingham. London ServiceDepot:-Webb's 14 Soh,, St. W I. Glasgow 1 /6Service:-J. R. Hunter, 138 West Nile Street.

1935 EDDYSTOSHORT WAVE MANUAL

bYou kr Height rincre as e din 14 days o money

Stabbing System soonbrings 3-5 inches

increase and new energy. The first, original, andthe one GENUINE GUARANTEED Height IncreaseSystem. Recommended by Health and EfiCciencuComplete Course, 5/-, or Booklet free, privately,STEBBING SYSTEM, Dept. M.P., 28 Dean Rd., London N.W.1.

Do We Possess TheseAmazing Powers ?Can Men and Women Attain the Acme of

Health, Success and Happiness Through thisRemarkable Formula ?

" There is a limitless, reproducing and ever-increasing force within every human, the powerof which will completely alter the character,develop a striking personality, break theshackles of mediocrity, and enable men andwomen to step out into the world and getwhat they want." This is the astoundingdeclaration made by Mr. Shelley Castle, thewell-known advocate of modern common-sense

psychology.

Mr. Shelley Castle

Indeed it seems revo-lutionary but neverthe-less proven by thosewho have tried andactually got what theywanted.

Mr. Castle refuses tobe considered as theauthor of an experimentor the promulgator ofa theory. He eschewsany connection withmystery or magicand states bluntly thatit is only commonsense equipped withthe instruments to forceits use-that only hardfacts should be givencredence.

Five thousand men and women are invitedto test the new formula free of charge. It isonly necessary to send your name and address(no money) and ask for a copy of " The GreatDiscovery." Address your letter to SHELLEYCASTLE (Suite 149), Castle House, Jacksons'sLane, London, N.6. You will receive theformula in simple, direct wording.

MONEYMAKIN

REVIEWEDBY OUR

PATENT EXPERT

NON-SKID TYRES" I should esteem it a favour if you

would kindly advise me upon the under-mentioned proposition :-

" The idea is to affix a thin spring steelpattern round the periphery of motor tyresand any other tyres, such as cycles, etc.They are fitted in the first place when thetyre is deflated, and when fully inflated thepattern fits snugly into the tyre, makingsame quite non-skid, unpuncturable, andpractically making it impossible for the tyreto wear out. The pattern does not interferewith the resiliency of the tyre, and can beattached to a tyre which has no tread,thereby rendering same as good as new.

" I estimate that twelve will be neededfor each tyre, and the method of attachingthe pattern to the tyres has been adoptedfor simplicity, but it could be made apermanent fixture to the spoke.

" The idea works well, but I am wonderingwhether I am up against legislation in anyway ; if not, would you advise as to methodof exploitation, and whether patentable."(F. C., Brixton.)

This invention is novel so far as is knownfrom personal knowledge, and forms fitsubject -matter for protection by LettersPatent. The inventor is advised to filean Application for Patent with a Provi-sional Specification, as being the leastexpensive method of obtaining protection.By such means he will obtain abouttwelve months' protection, during whichtime he can test out the invention andendeavour either to market the invention,obtain financial assistance to do so, or tryand interest tyre companies or othermanufacturers to place the invention onthe market.

Unless the inventor has actually testedthe invention in practice, he is advised todo so, as there appears to be some doubtas to whether it will effectually preventskidding of a wheel to which it is fitted.It should certainly minimise the chancesof tyre punctures. It is not thought thatthere is any legislation to prevent the useof such a device, in view of the fact that" Parson's " non-skid chains have longbeen used, which would appear to be morelikely to injure the surface of a road thanthe applicant's invention.A GREYHOUND TRAP

" I am forwarding you plans of twoideas that I have thought out, and wouldbe pleased if you would look them over andlet me know if you think they are at allpractical, as I am not an engineer. The firstis a greyhound trap,' and the second is anair current chamber to be used for the verti-cal rise of aircraft. I would also be obliged(if these ideas are not practical), if youwould point out to me where they are atfault." (J. C., Isle of Man.)

(1) The suggested improvement in grey-hound traps is not considered to be animprovement on existing traps, but thisopinion might be modified on consulting anexpert in greyhound racing, about which

we must confess very little interest. Theidea doubtless could be so designed as towork effectively, but even if such a devicehad no serious drawbacks, it is not con-sidered a commercial proposition in viewof the cost of present traps. Provided it isnovel, it could be protected by Patent,which is apparently the only means bywhich it could be protected, and unlessprotection is obtained it is not possible tomake money from the idea.

(2) The suggested arrangement for caus-ing aircraft to rise vertically is not veryclear from the description and sketches.Apparently the idea is to rotate a paddle-wheel within a semi -circular casing ; if so,the invention is based on a fallacy ; theonly result will be air disturbance withoutproducing any lifting effort.ELIMINATING SOAP WASTAGE

" I have designed a device for bathroomsor sinks, which will absolutely eliminate soapwastage.

" The appliance is attached loosely to thefaucet of the tap, thus allowing it to beswung aside when not in use.

" It can be inexpensively manufactured,and should prove a success if placed with asuitable firm.

" The device is unpatented as yet, but Iam now attempting to do so.

"Please give me your advice and opinion."(J. G., Forest Gate, E.7.)

The improved device for preventingwaste of toilet soap is novel so far as isknown from personal knowledge, andforms fit subject -matter for protection byLetters Patent. The inventor is warnedthat by submitting the device to manu-facturers before filing an Application forPatent he runs a certain risk, since publica-tion or showing the invention beforeprotection is ground for invalidating anyPatent subsequently granted for the inven-tion. Although the invention may benovel and patentable, it is considereddoubtful whether it would meet withcommercial success. It is thought that theperson who would be sufficiently carelessto leave soap to soak in water would notbe likely to take the trouble to manipulatethe clip to attach the soap tablet.A SPRUNG SADDLE ARM

" I have designed a sprung saddle arm,or pillar, for a cycle, and I would be verypleased to have your advice. Being only ayouth of nineteen, my knowledge of patentlaws, etc., is very limited. I shall thereforebe very pleased if you will enlighten me onthe following question :-

" How can I find out if the idea is novel ?" I think that you will agree that my idea

would add greatly to the comfort of cycling,especially if fitted to the very popular racingmachines, which are fitted with small non -sprung saddles." (A. G., Forest Gate.)

The proposed spring pillar for cyclesaddles is, from personal knowledge, knownto be old. Similar spring saddle pillarswere in use, and probably patented, somethirty years ago.



PRACTICAL WU Ef.4.HANEz5

ifezed-th,CZ twee

If a postal reply is desired, a stamped addressed envelope must be enclosed. Every query and drawing which Issent must bear the name and address of the sender and be accompanied by the coupon appearing on page iii ofcover. Send your queries to the Editor, PRACTICAL MECHANICS, Geo. Newnes Ltd., 8-I I Southampton

Street, Strand, London, W.C.2.

RE -SILVERING A MIRROR" Can you kindly advise me what material

to use for replating a mirror, and how to applysame to the glass ? " (W. M., Chelmsford.)

According to the "Handyman's 1,000Practical Receipts" the back of the mirrorwill no doubt be painted, and this paintshould be removed with a strong caustic sodasolution. The glass should then be treatedwith strong nitric acid, which will dissolveoff the silver. The glass should be madechemically clean with the soda and nitricacid, and then rinsed several times withdistilled water and laid on its edges. Itmust on no account be handled on the faceor dried, as the least particle of dust orgrease will entirely spoil the deposit ofsilver. For silvering the mirror preparethe following solutions : (1) 90 gr. ofnitrate of silver, 4 oz. of distilled water ;(2) 1 oz. of pure caustic potash, 25 oz. ofdistilled water ; (3) 4 oz. of milk of sugar inpowder, 5 oz. of distilled water. Take2 oz. of solution (1), add ammonia drop bydrop until the precipitate first formed isjust dissolved, add 4 oz. of solution (2), andthen ammonia again until the solution justbecomes clear ; make up to 15 oz. withdistilled water, then add solution (1) dropby drop until a slight grey precipitateappears, which does not redissolve, allow tosettle, add 2 oz. of solution (3), and stir well.The glass plate should now be carefullylevelled until it is exactly horizontal, andthe solution prepared as above should bepoured gently on the glass, so that the wholeof it is covered and none of the solution islost. Allow to stand several hours in awarm room free from dust. At the end ofthat time pour off the liquid, replace theplate, and pour on it a second quantity ofliquid. When the silver has deposited fromthis, rinse the plate in distilled water, allowto dry spontaneously, and then give a coatof good paint to form a protection.

OBTAINING AN OXYGEN SUPPLY" Will you please tell me how to make

a supply of oxygen uncontaminated by anyother gas, at a minimum of expense ? Ihave in mind electrolysis. In this method,is it essential for the wires to be of platinumand also in the interests of purity, would itbe better for the water to be slightly brinyinstead of acidulated ?

" Again, would a 6 -volt motor -cyclebattery be O.K. for the current supply ?

" The main requirements are purity andeconomy." (A. C., Rochester.)

Although electrolytic oxygen fulfils therequirement of purity, querist would findit a tedious job to produce any quantity bymeans of a 6 -volt accumulator. Such aprocess would never be used commercially.Surely for economy nothing can beatBrin's method. Barium oxide is heated inair to about 500°. The heating is thencontinued in a chamber to 1,000°, when

oxygen is liberated and may be collected.The oxide is allowed to cool in air to about500°, when it again absorbs oxygen, whichin turn may be liberated by repeating theheating to 1,000°. The process may berepeated indefinitely.

If the heating presents difficulties, aquick, cheap method of obtaining oxygenis to obtain a quantity of " 20 volume "hydrogen peroxide solution, acidulate itwith a few drops of sulphuric acid, and adda little potassium permanganate solution.Oxygen is abundantly liberated.

A quick, convenient method is to use anacetylene generator and sodium peroxide.A little of the latter is placed in the com-partment usually occupied by the carbide,and water allowed to drip through on to it.Oxygen is delivered at the outlet pipe.A FILTER FOR RAIN WATER

" I wish to make a filter for rain water,so as to make it fit for drinking. I have beentold animal charcoal powder is suitable, andwould like your advice on how to use this.I have thought of sinking a well, but under-stand that the water contains a lot of iron.Can anything be done about this.? " (W. B.,Devon.)

Efficient filtration, unless operated bymechanical means (that is, pressure filtra-tion) is necessarily slow ; animal charcoalin powder is extensively used in filtercharges on account of its adsorptiveproperties. Such charges can be purchasedat any laboratory fitters, and can be readilydropped into place in the filter chamber.We cannot vouch that filtration throughcharcoal would free rainwater of acquiredbacteria, although it would remove absorbedgases and debris. We consider that thepasteur filter would be far more effective,although slower.

Regarding the proposed well-any ironpresent in the water as hydrated carbonatemust be removed if the water is to be usedfor washing clothes ; this is accomplishedby the addition of washing soda and boraxstirred until dissolved and left for a fewhours in order that precipitation of the ironmay be complete before either the soap orgoods are introduced ; if the soap isdissolved before or with the alkali, it willtake part in the precipitation and givesticky particles containing iron and calciumsalts of the soap acids. These stickyparticles would subsequently oxidise andcreate iron -mould in the fabric.PHOTO-ELECTRICS

" With reference to your article onphoto-electrics, I have made, as instructed,a wet cell, with the two copper plates wellcleaned.

" On connecting it in series with a pairof 'phones and an accumulator, I obtainedno result.

" I took a voltmeter reading and it read1 volt. Putting a 50 -watt lamp an inchaway made no difference.

There was a younghubby named Lunn

Claimed HE was aborn plumber's son!

And we're bound to relate-He kept a real

plumber's mate-Always handy-aFLUXITE SOLDERING GUN!

See that FLUXITE is always by you-in thehouse-garage-workshop-anywhere wheresimple speedy soldering is needed. Used for30 years in government works and by theleading engineers and manufacturers. Of allIronmongers-in tins, 4d., 8d., 1/4 and 2/8.Ask to see the FLUXITE SMALL -SPACESOLDERING SET-compact but substantial-complete with full instructions, 7/6.Ask also for Leaflet on CASE -HARDENINGSTEEL and TEMPERING TOOLS with FLUXITE

THE FLUXITE GUNis always ready to putFluxite on the soldering jobinstantly. A littl: p essureplaces the right quantity onthe right spot and one charginglasts for ages.

The Gun also serves forgrease as an oil -can does foroil. Price 1/8.

ALL MECHANICS HAV

FLUXITEIT SIMPLIFIES ALL SOLDERING

WRITS "OR FREE ROOK ON THE ARTOF :OPP " SOLDERING-Dept. P.M.

FLUXITE LTD., DRAGON WOMEN BERMONDSEY ST.. S.E.1

An Absorbing HobbyAnothermodel to

fascinatingbuild is the

STUARTCentrifugalPump.

For afountain inthe garden,

etc.

Complete set of Castings and allmaterials, including instructions 6/6

Finished Pump - - 20/ -Electrically driven £4 : 7 : 6

Full description of this and allStuart models in Catalogue No. 3,72 pages, profusely illustrated,

6d. post free.

STUART TURNER LTD.HENLEY - ON - THAMES



am.

PATENTS,TRADE MARKSAND DESIGNS

ADVICE, HANDBOOKAND CONSULTATIONS

FREE!KINGS PATENT AGENCY LTD.Director: B. T. King, c.r.u.e., Reg. Pat. Agent G.B.,

U.S.A. k can.146a Queen Victoria St., LONDON, E.C.4and 57 Chancery Lane nearPatent Office), W.0.2.

49 Years TELEGRAMS:a GeoLoom, LONDON.References. PHONE: CITY 6161.

PRACTICAL HINTS ON PATENTINGand the development of inventions.

Sent free on application.

THE IMPERIAL PATENT SERVICEFirst Avenue House, High Holborn, W.C.1.

Preliminary Consultation Free.

FROST & CO.70 Old Compton St., London, W.I

Engineers, Tool and Model Makers.Models of all descriptions.

Inventors, Scale and Advertising.Patterns, Castings, or Finished Parts, Small

Stampings and Press Tools.Experimental and Repetition Work.

PATENTS, DESIGNSAND TRADE MARKSA VALUABLE GUIDE ON INTERNATIONAL

PROTECTION OF INVENTIONS.100 Pages - - Post Free, 6d.

The TECHNICAL ADVERTISING AGENCY253 (D) Gray's Inn Road, London, W.C.1

ROSS for HEIGHT/11.131.11.T8 SPEAK for THEMSELVE No Appli-Pupil, men*, gains V Ins. in 8 wks. antes - No

21, 5 ins. in 5 nibs. Drugs. No.. 20, 81 ins. in 16 dye. Dieting.

80, 2 ins. in 4 wks.40, 11 ins. in 6 ROSS SYSTEM

Increased my own height to 6' 3r. NEVER PAILSHundreds of Testimonials from all over the work/Pee: £2 Se. complete. Details free. Write NOW.

,MALCOLM ROSS, HEIISOPUEGCIA L I SaT

HAVE YOU A RED NOSE?Send a stamp to pay postage, and you willlearn how to rid yourself of such a terrible

affliction free of charge.Address in confidence-

P. TEMPLE, Specialist,"Palace House, 128 Shaftesbury Avenue, W.1

(Est. 30 gears.)

Send to FOYLES IFOR BOOKS !

New and second-hand books on every subject.Over two million volumes in stock. Catalogues

free on mentioning your interests.119-125 Charing Cross Road, London, W.C.2

Telephone-Gerrard 566o (ten lines).

ELECTRICAL ENGRAVING MACHINEFOR WRITING, DESIGNING ON METAL. ETC.Aluminium frame, pure silver contacts, Power-ful 2 v. model. Stand and switch, 3/6 extra.

45 a. accumulator, 5/9.MATERIALS & MACHINERY FOR DRY BAT-TERY MANUFACTURE. Rock bottom prices.

10/6Technical information free. List, lid. stamp.We design and manufacture hand machinesfor small repetition work. All trades.Post Inquiries invited.

Free E. H. GILES (Dept P.M ), 310 MARXHOUSEC.O.D. ROAD, LONDON, E.17.

BLUSHINGFREE to all sufferers, particulars of

a proved home treatment thatquickly removes all embarrassment, and per-manently cures blushing and flushing of theface and neck. Enclose stamp to pay postageto Mr. M. Temple (Specialist), PalaceHouse," x28 Shaftesbury Avenue (2ndFloor), London, W.I. (Est. 3o years.)

" Why should it read 1 volt ?" Could you tell me my mistake "? I tried

it with an amplifier and a 60 -volt polarisingbattery.

" Please could you also tell me the bestmaterial for making loudspeaker cones ?

" Is a screen -grid input to an amplifieradvisable ? and is it better than an ordinaryL.F. valve ? Would an H.F. screened griddo (Mullard PM12) ?" (W. M. L., Bishop'sWaltham.)

Many experimenters have difficultieswith the working of simple (photo -cells ofthe liquid type at first, but, after experiencehas been gained, these troubles pass away.

Your difficulty with the copper cell whichyou have constructed may be due to severalcauses :-

(1) Are you sure that your solution ofcopper sulphate in which you " formed "the copper plates was not stronger than1 per cent. copper sulphate ?

(2) Are you sure, also, that the twocopper plates forming the cell are nottouching each other but are kept apart bythe plate of ebonite between them ?

(3) Are you sure that the " window " inthe box in which the cell is placed is aneffective one ? That is to say, are yousure that the window does not allow light toobtain access to both sides of the cell at thesame time, instead of only to the one side ?

The above points must be carefullyattended to, otherwise the cell may probablynot function.

You do not require an accumulator inthe circuit. It is obvious that if you includean accumulator in the circuit, current willleak through the liquid in the cell, thusgiving a very appreciable voltage reading,as you yourself have discovered.

What you want to do, having first ofall attended to the above three points, is toconnect a pair of headphones directly to theoutput leads of the cell, that is to say,without the interposition of any battery oraccumulator.

You ought then to get a result, using a50 -watt lamp. If the cell is but poorlyformed, however, it will require the intenseillumination of burning magnesium to givea result.

You can, of course, employ a radioamplifier in place of the 'phones. This willenable the clicks " resulting from theintermittent illumination of the cell to beheard at loudspeaker strength.

The best material for loudspeaker conesis coarse linen cloth. This should be welldried in a warm oven and then varnishedwith any convenient varnish in order torender it more rigid and, also, moisture -proof.

For the simplest working in an ordinaryamplifier, the usual L.F. valve is to berecommended, on account of its relativecheapness and efficiency. In certain cir-cumstances a screen -grid valve may bepreferable, but without further details itis quite impossible to give any definiteopinion.

PLOTTING A GRAPH" In your June issue you published a

graph of the flow of water over a V notch of90 degrees. Would you please send me theformula for plotting the graph, as I have justcome in contact with a measuring notch of60 degrees which formula seems to carry a lotmore gallons per minute than the 90 degreenotch published ? " (P. C., Norfolk.)

Regarding the flow of water over a " V "notch, the graph given in our article in theJune, 1934, issue of PRACTICAL MECHANICSwas based on information given in " Moles -worth's Pocket Book of EngineeringFormula3."

MICROFU GOLD FILM FUSES<10

Specified for the" MONARCH "TWO VALVERYou need one Type F2,100 m/A Fuse an d

Holder.

20 Stock Ratings.Type F.2, suitable for Batterysets, 150 m/A blows at 300m/A. Resistance 7+ ohms.Voltage 260 Volts D.C.Type F.2, suitable for Mainssets, 600 m/A blows at I amp.Resistance 14 ohms. 260 VoltsD.C. Now FUSES 6d.available 2

4/-, 1 HOLDERS 6d.m/A, 4/6.

MICROFNES LTD., 4 Charterhouse Bldgs.,Geswell Rd., London, E.C.1. 'Phone : (ILE 4049 "se

CASTING MOULDSMake your own lead soldiers, animals,

Indians, etc.Illustrated Catalogue free.

d. Toymoulds,18 Kenyon M., Birmingham

NERVOUSNESSEvery nerve sufferer should send for my interesting book,which describes a simple, inexpensive home treatment forSelf - consciousness, Blushing, Depression, Worry, Insomnia.Weak Nerves, Morbid Fears, and similar nervous disorders.This wonderful book will be sent in a plain sealed envelope toany sufferer without charge or obligation. Write NOW andlearn how to conquer your nervousness before it conquers you.

HENRY J. RIVERS gteltillittntit'472.1

THE SECOND ANNUALSKYBIRD LEAGUE RALLYAND MODEL COMPETITION

THISinteresting event open to all

members of. the Skybird League will beheld from April 11th to the 20th. In addi-tion to the Club competition for theChallenge Cups there will be an open com-petition for individual members, both Cluband Associate. Captain W. E. Johns,Editor of Popular Flying, has kindly con-sented to make the final decision in judgingthe competition. Full particulars and con-ditions are published in The Skybird maga-zine, February and April issues. The latestdate for dispatch of models will be April5th. The winning models will be exhibitedat Hamleys, Regent Street, from April 11thto the 20th. The Presentation of Trophiesand prizes will take place at the Poly-technic, Regent Street, on Tuesday,April 16th, 2.30 for 3 p.m. Sir HarryBrittain, K.B.E., C.M.G., eto., Presidentof the Skybird League, will make thepresentations.

Captain J. Lawrence Pritchard, Secre-tary of The Royal Aeronautical Society,will give a lecture on " The Aeroplane andits Uses " (illustrated with slides). Admis-sion will be by ticket on application toSkybird League Headquarters.

A. J. HOLLADAY & CO., TAD.

WESLEY AIR PISTOLSMarvellouslyaccurate fortarget practice.No license required to purchasesSenior 45/-, Mark 1 30/-,Junior 20/-. Entirely British.Write for Litt. WESLEY & SCOTT LTD.,108 WEAMAN STRIGKT, BIRMINGHAM, ENO*

WHEN REPLYINGTO ADVERTISERS, PLEASE

MENTION'PRACTICAL MECHANICS'


CLASSIFIEDADVERTISEMENTS

Private or trade announcements can be inserted inthis column at the price of THREEPENCE per wordPREPAID.All communications should be addressed toTHE ADVERTISEMENT MANAGER,

NEWNES PRACTICAL MECHANICS,8/st SOUTHAMPTON ST., STRAND,

LONDON, W.C.2.

TO BECOME a Sanitary Inspector, Weights,Measures Inspector, Woodwork or Metalwork Teacher,School Attendance Officer, etc., write, ChambersCollege, 335 High Holborn, W.C.1.

CINEMATOGRAPH FILMS.-Standard size from6d. 100 feet. Machines, Accessories. Sample Films,1/- and 2/6 post free Catalogues free.-" Filmeries,"57 Lancaster Road, Leytonstone, EAU

NEW 3 -INCH Precision, Toolroom, Back Geared,Screw Cutting Lathes. L6/716. Photo. Stamp.-John P. Steel, Bingley.

SUPER A.C. MOTORS. All sizes at bargainprices.-A. Musham, Killinghall Road, Bradford.

STAMPS FREE!! Twenty Unused, Colonials," Neurope", H. Barnett, Limington, Somerset.

YOU CAN USE YOUR SPARE TIMEto start a Mail Order Business that quickly brings you afull-time income. Follow the lead of others who areaveraging EI2 per week net profits. Get away from adrudging routine job-join the big -money class. Noprevious experience necessary. Few pounds capitalonlyneeded. No samples or outfits to buy; no rent, ratesor canvassing. New method makes success certain.

Write to -day for FREE BOOKLET toBUSINESS SERVICE INSTITUTE, Dept. 885a,

6 Carmelite Street, London, E.C.4.

MAKE METAL TOYS I Easy, profitable, with"SUCCESS" Moulds. List Free.-LEE'S, BEN-TINCK ROAD, NOTTINGHAM.

INVENTORS' and ENGINEERS' Drawings,Models, Patterns.-Bland, 105a Crawford Street,London, W.1.

MOVIES AT HOME. How to make your ownCinema Projector. Particulars free.-Moviescope (N),116 Brecknock Road, London.

SMALL PRINTERS.-Cut-Paper Service for smalljobbing Printers. Handbill blanks from 1/- 1,000.Other papers and cards equally cheap. Sample Set senton application.-COLDBECK, LIVERPOOL ROAD,LYDIATE, LIVERPOOL.

£5 5s. Od. LOCOMOTIVE 37/6. NEW illustratedcatalogue secondhand models 41d. Models bought.-Central Handl ' Supplies, 11 Friars Street, Ipswich.

VACANCIES for 500 BOYSThe ROYAL AIR FORCE requires 500 boys of

good education (who must have attained age of 15 andbe under 17 years on 1st August, 1935), for training asaircraft apprentices in skilled trades. No experiencerequired. Good training, pay and prospects. Examina-tion at local centres. Particulars from Royal Air Force(Dept. P.M.), Gwydyr House, Whitehall, S.W.1.

A MAGAZINE of Electrical Progress. Amazingdevelopments in Electrical Engineering are rapidlyrevolutionising industry and bringing new benefits tothe whole community. To keep in touch with allthe latest in Electrical progress read this live Maga-zine. Written by experts, it is indispensable alike tothe technician and the ambitious student, while the"layman" will find it full of interest and inspiration."THE PRACTICAL ELECTRICAL ENGINEER."1/- monthly." Obtainable at all Newsagents andBookstalls, or by post 1/3 from George Newnes Ltd.,8-11 Southampton Street, Strand, London, W.C.2.

THE ONLY BOOK of its kind. Compiled by anacknowledged expert, this volume forms a completeguide, in alphabetical order, to the construction,operation, repair, and principles of every type ofwireless receiver, with a special section on television,and complete instructions on the making of variouswireless components. 392 pages, 490 illustrations."The Wireless Constructor's Encyclopaedia." By F.J. Canon (Editor of "Practical Wireless ").Obtainable at all Booksellers, 5/-, or by post 5/4 fromGeorge Newnes Ltd., 8-11 Southampton Street,Strand, London, W.C.2.

FREE ADVICE BUREAUCOUPON

This coupon is available until April 30th,1935, and must be attached to all letters con-

taining queries.PRACTICAL MECHANICS, APRIL, 1935

All applications respecting

-SOUKS worth01 ENDING

The Styles of English ArchitectureBY ARTHUR STRATTON. Published by

B. T. Botsford Ltd. A series of walldiagrams for schools, etc., with explanatoryhandbooks. Series I.: The Middle Ages,13s. net (paper) ; £1 12s. net (mounted).Series II.: The Renaissance, 12s. net(paper) ; £1 108. net (mounted). Studentsof architecture have here at their disposaltwo excellent series of wall diagrams toguide them in dheir studies of English styles.Those who study alone may consider thatthe explanatory handbooks containingsmall-scale reproductions of the walldiagrams may be sufficient for theirpurpose. These may be obtained separately,price Is. 6d. net (paper wrapper), or 2s. 6d.net (bound in cloth) each. There must bemany otherwise well-educated people whowould like to feel a little more sure of theirground as regards the differences between,for instance, Anglo-Saxon, Norman andPerpendicular styles of architecture, and tothem particularly these well -illustratedbooklets may be recommended.

Design in WoodworkBy PERCY A. WELLS. Published by B. T.

Botsford Ltd. 6s. net. Now that there is apersistent demand for better design inindustry and commerce, the foundationsfor it should be laid at the offset, during theperiod of training. " All things made foruse should do their job well," says theauthor of this readable book, " as with asaucepan, a spade, or a typewriter . . . butin things of permanent human interestfitness should combine beauty-that is,good design-with utility. A chair may becomfortable and still be ugly in form, inwhich case it does not completely suit itspurpose, for it should add its quota ofbeauty and dignity in a room." The secondprinciple is sound construction, whichincludes the right use of material. In thiswell -illustrated book will be found a soundguide to woodwork construction for all whoappreciate simple beauty in everyday things.The construction of articles in wood atevery stage, from the simple and elementaryto the far advanced, is admirably dealtwith.

Drawing, Design and CraftworkBy F. J. GLASS. Published by B. T.

Batsford Ltd. Third edition. 12s. net.Not only is this authoritative book magnifi-cently illustrated-it contains no fewerthan 2,000 illustrations on 52 plates,including 20 in colour-but it is also mostinterestingly and even fascinatingly written.The outcome of some fourteen years'teaching experience, it was first suggestedby the author's work in connection withthe training of teachers. His advice tothem to keep the student interested, iscarried into practice in each succeedingchapter, the subject being dealt with in soattractive a way as to whet the appetite ofany student to improve both his concep-tions and performance of artistic work.The book will be found of special interestto those interested in the elements ofdesign and ornament with a view to thepractice of Industrial Art. It will com-mend itself no less to students of every typethan to teachers and lecturers.

FREE SERVICE

FOR READERS

READERS requiring infor-mation concerning goods or

services advertised inPRACTICAL MECHANICSshould give names of Advertisersfrom whom particulars aredesired. Any number of namesmay be included and we willobtain for you catalogues, lists,and any other information youmay be wanting. THERE ISNO CHARGE FOR THISSERVICE.

Readers desiring particulars from anumber of Advertisers will, by thismethod, save time and postage. Half-penny stamp only is required if yourenvelope is left unsealed. If any Adver-tiser stipulates that stamps or postalorders are necessary before samples orcatalogues are sent, please enclose thenecessary amount with your instruc-tions. You are cordially invited tomake full use of this Service.

Post this to

ADVERT. SERVICE DEPT.,

PRACTICAL MECHANICS,

8-11 SOUTHAMPTON STREET

STRAND, W.C.2

Please obtain and send to meparticulars from the Advertisersin your April issue whose namesI give on list attached.

Advertiser Page No. I Information Required.

Attach sheet of paper, with par-ticulars, and your name andaddress (written in BLOCKletters), with date, to thisannouncement.

Advertising in this Publication should be addressed to the ADVERTISEMENT MANAGER, GEORGE NEWNES Ltd.,8-11 Southampton Street, Strand, London, W.C.2. Telephone: Temple Bar 7760.


Reconcilesselectivity

with quality!

Sharpest tuning receiverever described for homeconstructors!

THE 1935 A.C. Stenode " is the last wordI in super -selective, super -sensitive, long-

range receivers. It employs the remarkableStenode principle in the development of which" WIRELESS MAGAZINE and Modern Television "has been the pioneer. All -mains operated.Very large undistorted output. Provisionfor gramophone pick-up. Described in fullin the April number of WIRELESS

MAGAZINE and Modern Television."

Other big features in the AprilWIRELESS MAGAZINE and

Modern Television

Complete Guide to Car Radio in 1935

Tuning and Selectivity

Tests of Five New Sets.

Problems of Short -Wave Amplification.

THE APRIL

WIRELESSMAGAZINEAND MODERN TELEVISION

80 BigPages !

Now on Sale atall Newsagentsand Bookstalls 1

WHAT ISTELEVISION?

Explainedso YOU can

Understand it !LEAD TO DI -POLE AERIAL

PADOULATION ELE&TACCE

CATHOOE GUN DEFLECTOR PLATES

POWER R.CIAS ANDDOUNLE TPAE ELL SES

CATHODE -RAT TUBE

,1111111 BSI

TELEVISIONPICTLREAPERTURE

FRONTFl inow-ENTSCREEN

SOUND FAG*RECEIVER

CONTROLS

VISION RADIORECEIVER

WHAT is Television ? Everyone wantsto know to -day, because very soon

we shall have in our homes receivers likethe one shown in the clever illustrationabove-sound and sight all in one cabinet.But how is this possible ? PRACTICALTELEVISION tells you in language youcan understand. And PRACTICALTELEVISION is the one magazine keepingyou in touch with everything that is

happening in the realms of the thrillingnew radio miracle.

Special contents of the AprilPRACTICAL TELEVISION

* EXCLUSIVE ARTICLE BY J. L. BAIRD,AND TOUR OF THE BAIRD TELEVISION

STUDIOS

Ultra -Short Wave Television in NaturalDevelopments Colours

Some Disc ReceiverHints

Special Series for theBeginner

THE APRIL

PRACTICAL TELEVISIONNow on Sale at all 6DNewsagents and Bookstalls

Published by GEORGE NEWNES LIMITED, 8-11 Southampton Street, Strand, London, W.C.2, and Printed in Great Britain by THE WHITEFRIARS PRESS LTD.,London and Tonbrldge. Sole Agents for Australia and New Zealand-Gordon .16 Gotch Ltd. Sole Agents for South Africa-Central News Agency Ltd.


television made easy' building a 15c.c.model two … · 2019-10-23 · 140 persons, will be...

Documents