o32 Ch, il Enylneeriny.

Rieket t has made two others, introducing great improvements, being direct acting instea 1 (:,f'being driven by a pitch ehain. ():~e of these carriages has been built f,)v myself. I t weighs one ton : m d a half, a n d I h a v e had a speed of m,avlytwenty, miles a n h o m ' o u t (,f it. I gave a suggestion as t() the m.,le of placing the qxle in e.n,,~oxi~m with the driving gear, wld(.h I will explain. I placed the axle , i ' tile road wheel in radial se.,_,'mcnts, so that the springs rise and fall by 11,~ action of the road, the dvivinv" g(,:~r ,w t,~othed ~vh'eels are new,r a]!.wcd to be at a greater dista~,.e fl'om each other at any time ; the axh, as it rises or fidls perf'()rmi,7 a I)al'~ (,f a revolution round a m'::!;k shaft, on which is tlxed tim smallm" wheel which gives the "teflon to il~e road wheels. Its action is !,erf('ct. as the teeth ,d the wheels are aiways in gear to the same depth; alld the eonse~luenee is that the sprin._,'s act lnost perfectly, and it ~,~'s :ll.n~ the ro~d without trouble. I h'wo now had several trips ,,~l it from l}uekingham to Wolverto,.~, a d; ~tanee of ten miles, and this has been done within the hour inelu(lin~ st,,l,p:~gos.

.An,)ther advantage ,)f steam (~n roads over horse-power is, l}::~t in- stead of requirin 7 twenty, ov thir ty horses, t~ rming .qu i t ea tvo,,p, to take a carriage eontaillin_," some heavy weight, you place 1)(f(,ve the said carriage a steam engine. This power wi!I cost but a~:m:dl sum in eomp'~.rison with horses: it will be a constant power s~) hmg as it gets coal and water. I t will take up but little room, not being mud, larger than a eommon carriage. This seems a most important l'easor~ for the advaneement of steam, as at this present day saving of time, money, space, and at the same time gaining increase of" power, are co- gent reasons for advocating any eause.--d°roe. Brit. Assoc. 1860.

Horse Railways on G)mmon Roads.* :By JOtIN CRANE. To the Editms of the Mechanics' Magaz ine : - -

GENTLEMEN : i P e r f e e t ] y agreeing with yourselves and Messrs. Train & ]~urn in the advantages to be derived from horse railways, I humbly eraxe a corner in your able and liberal Magazine for a brief exposi- tion of my own views on a mere matter of debateable detail. I t strikes

Fig. 1. me that there is no need whatever ....... for the vehicles that run on rails

in public streets to have fl:mched wheels, which would prever~t their Funning except on such rails; but that the present wheels might be retained, provided all the axl~ trees

were made the same length, and a fi, 'm of rail adopted like that in Fig. Fig. 2. 1. I t nlay be called a. " t r o u g h rail ," at:d is

iive i tches wide inside, with two tlawches, and t,) be fixed on continuous hmg' tudinM

: wooden sleepers, or embedded in stone [)locks laid down at interwds of about flmr feet. I

:: also recommend a stone em'b to be laid along each side of the rail, such as is now general ly used for curbing

*From the Lend. Mechanica' Magazine, June, 1860.

Keystone for Arches of Stone. 23~

foot-paths. :But if a flanched wheel be preferred, then I think the form of the rail in Fig. 2 is better suited to meet the various requirements of the ease than any I have yet seen. Each could be made either of wro11,ditm o1" cast iron, and of' course of any dimensions to suit the par- tiellblr traffic. I will not now take up any more of your space or)-our readers' time by enlarging on the advantage of iny l~roposed plans, bu~ conclude by assuring you that--whether they are novel or no t - - I shall no~ patent them, but present them to the public gl'i~tuitously.

59 Lee Crescc,nt: l l i l l l l iUg l i a i n~ ) l ; t ) 31 s 1 ~,i;0.

For t i t " J i a l r l / : l ] of the l P l a n k l i n ] l l ~ t i t l l t l ' .

dVew Rule for D~Tt]~s ::t" _t(<,,q.stone ./;~r eitlter Seumentcd or Elliptic Arche,~. of St,,ne. By Joux C. T~:Au'rw~xE, C.E., I'hihlda.

I subnfit the following ol'igimd rule for detcrMning the dol)th of keyst ,ne for either segmental or elliptic ~n'chcs of ~tonc, as coincid- ing more nearly tharl tuly other with which I t~l,.1 acquainted, wi~h the practice Of the best eiighlcers :

i f of first class tilL-stone work o[" hlird nlateri'd take "30 of the s(tuare root of the radius tit the crown. ~Of second class work "4 ; ailt[ for brick or ruloblc arches "45 of the same square root.

The following exanlples will show the accordance of the rule with e-:istilig struetul'es both elliptic and segmental, in the first ca~% viz : with til's~ class work and materials.

• 3 O V / ~ s at crown.

Cabin J~)hn Aqueduc t and Rna( lway Arch ,~f the " IV; ts l l i l lg lo l l A, lUedt/ct .4:

(]POSVPIIOF ~t idgo, ~tOl'oSs Ih,, 1}12e~ . ]~,)iiClt)Ii l l r i , lge Ui l !w) . Tllal i l l2s~ (i[otit:t,sttq" ih ' id~e, ~t1%t.l'Jl~ C l a i x Brid~,e, FritliOc. 1 ])(iFH. T I l l i l l , N eu i l ] S, a~ d<'sigu~'d, . . 57cuillv :is it ('xi~l~ on a('C()lillt of the setth,-

lllCllt tit t | le arch(,... Lickill~; A, lm,duet , Ches. ~.nd'Ohio Caual~ " Sta iu ~ Ill idg~,, 1~o~ Bridgt!~ Eugland~

,~40llll('~lCy A qllell l l( ' i ; , l , l l g a r l iadllt'i-~ ~#'()tlalld 1 Ja)l l( '~ R i v , ' r ,~ll]llt, t l i teI . . ll(,a(IJn;~ Ibdhoml , at llt>illliil~ ~tqui-c i r(.lc, . . • l i t ) l i t N : l p , l c o n Y i a d n c t . I)~11"[~ l, Nll l f l ] l r t lb ] l lP

]IIH~IHIIFV i l l C(']ItI!III : l i t i t l f i p i y IQ" '45. ) i l i l d t ! l l l l c l td ~lria(lllO[~ b r i c k i l l ceB le t t t : l l l l l ] -

Spau Rise ]tad. at Ac tu ,d C,h :u i 'd in in (h',lwtI 1"~('~ ill Key ill

feet. li~ot, in Iiwt. feet. fi~ct.

ee,) 57!4 1-~4!4 4q0 4q7 2n0 4'.' l ~ t ) 4 ' 0 0 4'26 152 2!)!/~ 1~12 4'75 4"58 15(, ;;5 150 4"50 4 4 l J3() 5~ ~,2 3"10 5"20 ]40 lS ] t iO 4"00 4"53 128 32 i60 530 4'55

] 2<q 25,) 5'30 5't;9 90 ]5 ! 76 2"83 3'14 74 9"3 7~ - - ;J'uO-- 3'18 ,'56 I3'75 b l 250 3"2L-

I ! 51 9 l 50,1} 2'50 -'2"55 50 25"00 ' 25'0 2'ljl) l'SO ,JtJ 7 47"U 2"titi 2".i7 "1 ~ 2,;',k 1'66 1"~6 o "0 "00 l ' tJ I }':J3

115"5 1475 I 1 2 0 ' 4"00 4'93 i

Engineer .

M(.igs. i l a r r i s o n . ]~eimie. Tcl ibrd .

31oseit. ]*l~l.['Ollt]t,

]h ,rroilet. FiM;.

"d-aJker aIld: Burges , t

FJsk. Miller . I';IJ~'L ~a,ele.

Couch, ' .

t i l l v hv 45 128 24"'h-), 169"0 5"25 5"~45 r, rune l .

Our public works abound with cut-stone al'ehes having keys varying from "36 to "4 of' the square root of the radius of the crown, and with rubble arches having keys from "4 to "4<5 of the same square root; but I have not thought it necessary to introduce theln.

* T h i s is t lm la rges t st~me arch of modern t imes, or, perhaps, of an2," f ,n 'mer ])el'led, un less we excep t the a l ie ient lui t lge of ' i ' rezzo. ,~uid to have been 251 fi'et span ; it was dc~JgL,~.'d~ ttnd i ts erect ion Imperiut~.nde4 by Capt . 3lontgt~mery C. 31, igs~ of the U. S. Topog. E n g i n ee r s .

20*