SCIENCE-ADVERTISEMENTS

New Castle InCubatorChamber has uniformand constant temperature

The new Castle Incubator fills the need for areliable and accurate apparatus at a moderateprice.

The electric heater is beneath the bottom (nottaking up space in the chamber). It distributesthe heat uniformly from the bottom and main-tains an unvarying temperature.The automatic regulator controls the escape ofexcess heat up and out through the rear doublewall. The walls are made of thick insulatingmaterial, bound with polished copper.

Send full data on New Incubator No. 505

Address ...

Sterilizers for Physicians, Dentists and Hospitals No. 505. Inside: 12" high x 10" wide xWilmot Castle Co., 1212 University Ave., Rochester, N. Y. 121/2" deep.

Victor Inlterval Timer (;2 LabNEveryc or nervc iner ~~~~LaboratoryNeeds

with Automatic Alarm ItMeasuring time in periods ranging from

15 seconds to 2 hours

An essential factor in the proper

equipment of

Photographic Diet KitchensDarkrooms Hospital Wards

Scientific GymnasiumsLaboratories Class Rooms

Industrial Plants

PriceOver 30,000 in use!

VICTOR X-RAY CORPORATION

2012 Jackson Blvd., Chicago, Illinois

L II S~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~---~ Ii11

ix

0

SCIENCE-ADVERTISEMENTS xi

Marine Biological LaboratorySTAIN CHNOLOGY

Woods Hole, Mass.SUPPLY Biological Supplies A quarterly devoted to biological stains and

DEPARTMENT to microscopic technic closely relatedFor the classroom, museum or col- to staining.

Open the Entire lector.Look for the sign of the Limulus. Subscription price: $I.50 a year

Year As the Limulus represents the test Published by the Commission on Standard-of time, we feel from the businessjgrowth that our supplies have also ization of Biological Stains.stood the test of years. (First number appeared in January,

Se-nd tor Catalogue 1926. All back numbers are still4,J*.S'T°t No. I. Zoological and Embryolog- available.)

ical material. Life Histories andHabitat Groups.

No. II. Botanical material. BIOLOGICAL STAINS

A handbook on the nature and uses of theAddress all correspondence regard- dyes employed in the biological laboratory.

ing material and catalogue to:Supply Department By H. J. CONN

with the collaboration of the members of theGEO. M. GRAY, Curator, Executive Committee of the Commission on

Standardization of Biological StainsX Woods Hole, Mass. I5I pages, cloth bound.

.__ Published by the Commission.

IRAK Buy Good Binoculars Price $2.50 postpaid (io per cent. discount ifr S POCI,.t The now 7-Power Mirakel weighs only cash accompanies order).

040ClvAN_ 6 oz. Can be carried in vest pocket orladies' bag. A wonderful high-grade $35 Both the book and journal should be orderedPrism Binocular for every use..._Hensoldt New "Dialyt"-fx30-13 oz. direct of the Chairman of the Commisson:

Zeiss Wide-Angle "Deltrentis"-8x30. $66 H. J. CONNPrismiris Pocket Binocular, 6 Power,12 oz. prism ...... $16 Lock box 299 Geneva, N. Y.

Fiala Sleeping Bag-Scientifically Correct-Warm LightWeight-Sanitary. Best for Outdoor Sleeping ....... $e5

SPECIAL: "LLAMA" Fiala Sleeping Bag; used In New-foundland at 42 below zero; no fire, 2 man tent. All"filled" bags were thrown away. The Fiala bag can bewashed, sunned and dried. With cover completetweighs 5 lbs. 12 oz.; rolled bulk 17" x 7". Price X PHOTO,-LECTRILLSAnyone who does not mind bulk and weight, or where priceis an object, we can furnish a good "filled" bag at $12.50 up.

Scientific, Exploring, Camping Outfits-Write for Catalog A TI IEIC LlANTHONY FIALA, 25 Warren St., New York

Withlout Fatigue-Highly Sensltiveme Absolutely Reproducible-Instantaneous in Response

fly-Speed MixersClamp to any tank, operate from The BURT-CELL Is made by a new method andlight circuit, mix all kinds of liquids, should not be confused with any other photo-electric

Also used for even temperature * cell. By a special process of electrolysis, the photo-All Sizes baths. Thousands in use.

.1 from Write for circular. I electric metal is Introduced into a highly evacuated| 1/10 H. P. ALSOP ENGINEERIENG CO. * bulb directly through the glass wall of the bulb, giv-l

$37.50 up 47 W. 63rd St., New York ing photo-electric material of absolute purity. The

superiority of the BURT-CELL Is due to these fea-

hiran Tnnikno nnaiihlp rpailt.a noaver hfnre nhtninaible.l

THE SCIENCE PRESSPRINTING COMPANY

PRINTERS OF

SCIENTIFIC AND EDUCATIONALJOURNALS, MONOGRAPHS

AND BOOKS

Correspondence Inted

LANCASTER, PENNSYLVANIA

Lureti, lniiU^g yt>""s-uitu Krslulut ucrKtv UCLVrr VULICULAU"1.

Described In Bulletin No. 271

QUARTZ CELLS-We are pleased to announce thatwe are manufacturing reproducible quartz photo-cells for measurement of ultra-violet.We also manufacture the STABILIZED OSCILLO-

sCOPE-the only VISUAL OSCILLOGRAPH havinga linear time axis and no inertia-giving an accuratepicture of high freauency wave forms. This is a mostpowerful tool for the study of periodic phenomena.

Write for Bulletin 273

DR. ROBERT C. BURTManufacturing and Consulting Physicist

327 S. Michigan Ave., Pasadena, Calif.

SCIENCE-ADVERTISEMENTS

cANNOUNCEMENTA Scientific and Educational Book Service

THE SCIENCE PRESS DISTRIBUTING COMPANY is prepared to supply any book or any

journal published in any country at as low a cost as it can be obtained. It will also supply mono-

graphs, reprints and extracted articles as far as these are available. This agency has been estab-

lished for the convenience of men and women working in science and education and for institutionallibraries. It is particularly concerned with books, journals and reprints in science and educationwhere it can offer unexcelled service. Orders for other publications, however, will also be filled. In-

quiries and orders may be addressed to: The Science Press Distributing Company, Grand Central Ter-

minal, New York City.RECENT FOREIGN BOOKS

MATHEMATICS

Der absolute Differential-Kalkill (Lezioni dicalcolo differenziale assoluto) und seine Anwen-dungen in Geometrie und Physik. Tullio-Levi-Civita. German edition by ADALBERT DuSCEEE.310 pp. 6 illustrations. (Die Grundlehren d.mathem. Wissenschaften. Volume 25.) $5.25.

Elementarmathematik vom hoheren Standpunkteaus. FELIx KLEIN. Third edition. Volume III.Prazisions-u. Approximationsmathematik. 238pp. 156 illustrations. (Die Grundlehren d. mathe-mat. Wissenschaften. Volume 16.) $3.75.

Grtndzuge der Differential-und Integralrechnung.Fourth enlarged and revised edition. GERHARDKOWALEWSKI. 417 pp. 31 figures. $4.00.

Ecart, 6quilibre, balancement. Vessillier. 72 pp.Paper bound. $2.50.

ASTRONOMY AND METEOROLOGY

Le ciel et l'univers. Astronomie moderne.TH. MORnAUX. 640 pp. Illustrated. $7.25.

L'6thdronique et les archives de l'universm S.CHRisTEsco. 168 pp. Paper bound. $1.50.

Atlas Stellarum variabilium. (Specula Astro-nomica Vaticana.) J. G. HAGEN. Series VII: M.EscH and J. G. HAGEN: eas supplens stellas vari-abiles quae ad seriem VIm accesserunt. (11 starmaps and 41 pages of text. In portfolio.) $12.50.

PHYSICS

Handbuch der Elektnizitat und des Magnetimus.Edited by L. GnAETz. Volume V. 896 pp. $19.00.

Precis de physique d'apres les th6ories mod-ernes. A. BOuARIC. Second edition. 920 pp.736 illustrations. $2.20.Gesammelte Abhandlungen. ERNST ABBE. Vol-ume IV. Unveroffentlichte Schriften wissen-schaftlich-techn. Inhalts. Part one. DieEntstehung d. Glaswerks von Schott & Gen.nach gleichzeit. Schriftstiicken aus amtl. u.persbnl. Besitz zwischen d. Marz 1882 u .d. Jan.1885. 146 pp. $2.25.Dispersion und Absorption. GEORGE JAPFr. 65illustrations. Medien mit verinderlichemBrechungsindex. .6 illustrations. Lichtzer-streuung von Richard Gans, 7 illustrations. 430pp. (Handbuch d. Experimentalphysik. Vol-ume 19.) $10.25.

PHYSICS-Continued

Druckdifferenzen in stehenden Schwingungen alsUrsachen der Femkrafte. ALADLR GLASER. 179pp. Illustrated. Paper bound. $3.00.

AERONAUTICS

Die Grandlagen des Flugzeugbaues. 0. P. FucHs-WIEN. 146 pp. Illustrated. Paper bound. $2.25.

Grundzitge der Flugmeteorologie des Luftwegsnach Ostasien. HEiNRICH SEILKOPF. (Archiv d.deut. Seewarte.) 48 pp. 4 illustrations. 13plates. Paper bound. $1.50.

Jahrbuch der Wisonschaftlichen Gesellachaftfur Luftfahrt E. V. 1927. 188 pp. Ill. $5.00.

Luftfahrtforschung. Volume 1, part No. 2. pp.35-94. Illustrated. Paper bound. $2.90.

Trait6 th6orique et pratique de navigationahrienne. GRAFFIGNY. 310 pp. Paper bound.$1.75.

ENGINEERING

M6canique rationelle. BOGAzRT and VAN DrNDUNGEN. Volume I. 330 pp. Paper bound.$2.00.

Cours de m6canique profess4 & 1'Ecole SuP6ri-eure des mines. PAuL LMvY. 303 pp. Paperbound. $2.50.

Les Oombustibles dans l'industrie moderne.BERTHELOT. 500 pp. 100 illustrations. $5.10.

Distillation des combustibles a basse temp6ra-ture. Utilsation rationnelle des combustbles.R. COuRAu and HENRI BEssoN. 372 pp. 75 illustrations. Paper bound. $2.60.

Cours de mat6riel d'entreprises Gren6 et MalavaLVolume III: Installations de chantiers. 324 pp.Paper bound. $2.25.

Drang und Zwang. Eine hohere Festigkeitslehref. Ingenieure. AUGUST FOPPL and LuDwIGF6PPL. Volume II. 382 pp. 79 illustrations.$4.40.

Starkstrom-Technik. Edited by L. GWRT&z. 457pp. 475 illustrations. (Reprint from Handbuchder Elektrizitat.) $9.65.

q.

*. .