A Letter of Mr. James Short, F. R. S. to the Royal Society, concerning the Inventor of theContrivance in the Pendulum of a Clock, to Prevent the Irregularities of Its Motion by Heatand ColdAuthor(s): James ShortSource: Philosophical Transactions (1683-1775), Vol. 47 (1751 - 1752), pp. 517-524Published by: The Royal SocietyStable URL: http://www.jstor.org/stable/105101 .

Accessed: 23/05/2014 23:43

Your use of the JSTOR archive indicates your acceptance of the Terms & Conditions of Use, available at .http://www.jstor.org/page/info/about/policies/terms.jsp

.JSTOR is a not-for-profit service that helps scholars, researchers, and students discover, use, and build upon a wide range ofcontent in a trusted digital archive. We use information technology and tools to increase productivity and facilitate new formsof scholarship. For more information about JSTOR, please contact support@jstor.org.

.

The Royal Society is collaborating with JSTOR to digitize, preserve and extend access to PhilosophicalTransactions (1683-1775).

http://www.jstor.org

This content downloaded from 193.104.110.34 on Fri, 23 May 2014 23:43:50 PMAll use subject to JSTOR Terms and Conditions

LXXXVIIT X Leer of Mr. James Short, F. R. S. to the Royal Socicty, concernirg the ltirventor of he Gonteva?nse n the Pe- dglam of a (:lock, to praven the Irregala- rities oJ s Motioa ;.y Hegxt md Cold

Gentlemen,

Read Nour. 9, H E fubjeRc of converfatlon of late

752 1 havng c)iten turn'd upon that in_ genious contrslrancc in the persdulum of 1 clock, to prevent the inequa}ities in sts motion, arifmg from its diflRerent lenBhs, in diffierent feSons of the year, by the effcds of h>t and wld ; aizd it havmg been o*erx aIked, wlwo was tlse inventor of ita I hte ffierefore thought proper to drtw up the followiig hiitori->l account- of it * And as dlis tecount conta;as mthing but- matters of faft, fiupprted bsr the belk authorItiesa l hope st wiII be acceptable to this Socltty. I um

Y; mofic obedieDt humble fervant,

J Short

->00N after the xnvention of pendulum-cloctcs 3- (ju;0;ly afaibed to the celelirated Mr. Huygen-s), it was founds thwt they rw liaKe to conGderable inequalitses in; thet motion; vwhich were im-agined Z arsSe firom the pendulum, in it vilibtionsy de- iribing.an are of a circle; td, cmfeafuentlye that ihe lasger vlbratlxs mtlPc; be Xw¢r than the er

0zsW

[ 5I7 3

This content downloaded from 193.104.110.34 on Fri, 23 May 2014 23:43:50 PMAll use subject to JSTOR Terms and Conditions

[ 5I8 g

ones 1n order to remXedy this imperfedrion, tlle famo Mr. Huygens wrote a treatiCe,- called Borolo;ium oJ4- nllatorm (a piece of geometry} which does honour to the laR cBntury), in which he demonfirates, from tlle properties of tile cycloid that the vibrations of a

pdndulum, moving in a cycloid, would be performsd ln equal tiluesr even tho the vibrations were lln- equal. Pendululas therefore were made to vibrate in a cycloid; but gteat inequalities werc Itill obSerlrsd in- the motion of clocks.

We do IlOt read of any attempts) after thisX to re- gulate the motioll of clocks, till the year I726, WlltI

WIr Gcorge>Graham deliverld into the Royal Society a paper, which is pu61iShXd in the PJuil Eran/: Ns 392) in which he fays, that lt having been appre- hended, that the inequalities in the motion of clocks arofe from a charlgs of length ta the pendulumy by- the influences of heat and cold, hef about the year I 71s, made -feveral trials in order to dificoverX whe ther there was any confiderable difference of expan_ fion between brafi, i:leel, iron, filveq Sc. when es- pgfed to the fa£ne degrces of heat , cxceiving, that it would not be very didicult, by making uCe of two brts d metals differing conflderably in their degrecs of expanfion and contraftions to remedy, in grat meafilre7 the irregularitiesX to which common pen- dulums*are fubjedr. He fays alIb) thats from the experiments he then made, he foiilld their differ ences fo fmall} as gave him no hopes of fucceeding that iwayX vzhschomai him leave off profecuting this; affair any more at tha:t-time: That, fome tinat afiers having obServed an extraDrdInary dggxe of expanfion, by -heat, in quickillverX the thollght of a pro?er

- manner

This content downloaded from 193.104.110.34 on Fri, 23 May 2014 23:43:50 PMAll use subject to JSTOR Terms and Conditions

[ 5I9 3

manner of applying a column of it to the pendulum of a clock, in order to prevent the inequalities arifing Som its- different -lengths by the effeEts of heat ana cold; vlzhich fucceeded accordillgly, and is what is- now called Mr. Graham's quickfilver-pendulum.

Mr. GrahamX in the fame paperX takes notices that, tho' the pendulum of a ctock was to remaia invariable, yet there would Sill be fome irregulatities in the motion of the clock, arifilng from the f ldion of the different parts of the clockwork, and from the. different degrees of foulnefs.

In the year I72y, Mr. John Harrifon, cyf Barrowr in LincolnShire, made feveral experiments upon wires of diffierent metals, in order to find their- different degrees of expanf1on and contradrion: For he thought, that, by a proper combination of wires of two dif- ferent metals, differing confiderably in their expan-- fion and contradion,; he miglit be enabled to keep the centre of oticillation of a pendulum always at the fame diIlance from the point-of fufipenfion.: Inxcon- fequence of thefe experiments, he made a penduluma confiIlit of one Reel wire, at the end ot which is the bob or weight, and, on each fide- of this wire four wires alternately brafis and Iteel, fb difpofed and conirived, as to raife:the pendulum the fame quantity as it iS lengthen'd by heat, and to let down the pen- dulum in the fame proportion Fas it is raifed ;-by coldw - He fmade alfo a drawing of a clock, in which the wheels are difpofed in a dfferent manner fiin thoSe then: in uSe; which drawing I harre-fieen, flgned by himfelfin the year I72f. Two of thefe clyks -writh pendulums, as dercribed a-boves were finiffied in the par x726. In thefe clocks Mi. Harrifon has made

' puicuk

This content downloaded from 193.104.110.34 on Fri, 23 May 2014 23:43:50 PMAll use subject to JSTOR Terms and Conditions

r-52°3 a particular fort-of pallets, Ito as to be almotnc intirely free from fritition; for thoa he had thus happily fuc- ceeded in his conttivance to prevent the inequalities tn the motion of the clock,-arfing from tbe differexlt lcngths of the pendulllm by the effeflcs of heat and cold, yet he found there were confiderable errors flcill- remainillg, occa.fion'd by the fiiftion of the pal- lets, aF in the common way. He has alfo fufFended ehe pendlllum upcxn thx wall of the houSe, lntirely indepndent of the clock and clock-cafe: For he had obServed. confiderable alterations in- the going of the clsock, when the pendulum is fufpended as in thq com on manner. His pendulum ribrates in an arc of-about lS degrees, vsrith a-bob of-about three pomds, between cycloidal checks, which he. hsw felf found were nBceAry, tho' 12 hd never heard of M- Huyggns's book, till aRer he had made them. He has alfo dxrpofed the force of his p.endulum-wheet iipon tlie pendultim, by his fort o{pallets, in Iich a manner, -thagt the vibrations of the pendallum will ne & affedqd by the different relAltance of the air. UpXon th>e whol¢,. this clock i--s made in fach a man- ner, as - to be ali;noR intirqly firee from frid:ion ; in confequcace of which he uSes no oils and therefbre- ere is no neceElty earer to clean tlAe clock. NYhen he fettle4> in -LondOn, he Sent for one of theSB cloch fromVthq couptry, apd d it up in his houfe in ange Rreet, in the year l739, where it has -Rood esrer fince, and in-all that iime has n>rr variedabosre one minute firom the ttuth. h can dewna upon lt to a fescBnd insa month.

+About thq yeg 17>XW9 h{F. Harrifta made hls firA machine for meafurtng time -at fea, in which he has

- likewife

This content downloaded from 193.104.110.34 on Fri, 23 May 2014 23:43:50 PMAll use subject to JSTOR Terms and Conditions

[ 52I :|

likewifie applied this combination of wires of braEs and Reel, to prevent any alterations by heat and cold. In the year I726, he went on board one of His Majelly's Ihips of war with this machine to Lisbon,, and returned, where this machine was feen by every curious and ingeniou& perfon} who were pleafed to go to his houSe. Since that time, he has made two more of thefe machines ar clocks for keeping time at fea, in both which he has likewife this provifion, to prevent the effeds of heat and cold.

An ac-collnt of thefe curious mashines, and of the many ingenious contrivances which Mr. Harr;fon has made uSe ofg in them, for anfwering their intended purpoCe, and alSo an account of the fusceis of his voyage to Lisbon, and back again, is contained in an excellent fpeech o;f our worthy Prelident Martin Folkes:, Ffiq; upon his delivcring to Mr, HarriSon the gold medal of Sir GodErey Copley; which fpeech is inferted in the minutes of the Society in the year I749-

-Mr. John Shelton, who was the principal perfon employed by Mr. Graham in the making of aRrono- mical clocks, informs mes that Mr. -Graham, - in the year I737, made a pendulum confiting of three bars,, viz. one of Reel, between two of braSs} and that the lleel bar aded upon a lever, fo as to raife the pendu_ lum, when lengthened by heatX and to let it down, when ffiortened by cold. This lever, -which is very firong, reIts upon a roller; which roller is made moureable, fo as to adj!lIt the arms of the lever to their true proportion The whole was made to be as free from ;fEiEtlon, as pofl"ble) in fuch a conRrucw tionX Mr. Graham made obServationsZ by tran.fits of

U 11 u the

This content downloaded from 193.104.110.34 on Fri, 23 May 2014 23:43:50 PMAll use subject to JSTOR Terms and Conditions

[ 522 ] the fixed llars, of the motion of the clock with this fort of pendulum, and fi4om the experience offeveral years (during which the clock was kept conitantly going) he found, that the clock was liable to fudden I:'rarts and jerks in its motion. Of this he informed Dr. Bradley, Mr. Blifs, myfelf, and feveral other gentlemen. This clock Itill remains in Mr.Graham's houfie, in the poifeElon of his executors.

I have been informed, that one Mr Frotheringhams a quaker, of LincolnIhire cauSed a pendulum to be made, confiiting of two bars, one of braEs, and the sther of Reel, faften'd together by fcrews, with leO arers to raife or let down the bob; and that thefe Severs were placed above the bob. This clock I have feen, and was told by the maker, Mr. John Ber- ridge, that the pendulum of it was tnade in the year I738, or I-739, and that the dial-plate of it was engraved at Mr. SiSlson's houSe in the year s738: and this clock is in the pofl^efl lon of Mrs. GibSon, i2]

Newgate-llreet, who has had: it ever lince the year I739&

In the Ei/?. of the Royal Sca:d. -of Scienves at Pargs, for the year X 74 1, there is a memoire cxf M. Cafl lni, in which he defcribes feveral forts of pendulums for clocks, compounded of bars of braSs and Iteel} and applies a lever to raife or let down the bob of the pendulum, by the expanfion- or contradcion of the bar of braEs He has alSo given us, in the fame memoire a probiem for finding the proportion, which the two arms of the lever Ihould have, to an- fwer the intended purpofe; and alfo a demonkra- tiON of it-

n 6

This content downloaded from 193.104.110.34 on Fri, 23 May 2014 23:43:50 PMAll use subject to JSTOR Terms and Conditions

E 523 E In June, x7S2, Mr. John Ellicott garre in to the

Royal Society a papel^) containing the deScription of a pendulum) confi ing of two bars, one of brds, and the other of iron, fillened together by fcrews, with two levers in the bob of the pendulumX fo contrisrteda as to raife and let down the bob, by the expanf1on and contradcion of the braSs bar; and alfo to adjull the arms of the levers :to their true proportion $. He fays, that he firIc thought of thefe methods of apply- mg barsofbrafs and iron to prevene the irregularities of a clock, arifing firom the diffierent lengths of the pen- dulum, by the effedcs of heat and cold, in the year x732 ; and that he put this his thought:in executoR in the year T738.

In the year I743, I bought a clock of Mr. Graham, which he had kept going for two years before. This clock has a pendulum, compounded of wires of brafs and Itecl, in the manner of Mr. Harrifon's combina- tion. It has alfo a provifion in the bob, to adjui} the wires, in cafe they happen to be too long. When I -firll took notice of this contrivance or provirlon in the bob, I alked Mr. Graham l:he reafon of it; who told me, that, having obServed fome inequalities in the motion of the clock, he imagined,, that tlley arofe from the wires being fomewhat too long; and there-

Uuu 2 fore

* He has alSo given us in the fame paper another conflrudion of a pendulum to prevent the effeAs of heat and cold, confi0ing of two bars, one of brafis, and the other of iron; the brats bar afting upon a lever, at the end of which. is fafiened the pendulum, the whole fo confir ed and contrived, as to raiCe the pendulum, wlien it is lengthened by heat) and to let it dswn, when {hortened by cold.

This content downloaded from 193.104.110.34 on Fri, 23 May 2014 23:43:50 PMAll use subject to JSTOR Terms and Conditions

[ 524] fore added this contrivance, to adjuI} the lengt};fof the wires; but that, when he had done this, he fio-und inequalities Itill remaining; and therefore juRly concluded, that they arofe from the differexlce in the fxidcion of the different parts of the clockworks oc- cafioned by the differences iIl the fluidity of the oil, fCc.

From what has been lsaid above, it appears, that the improurement of clocks, by a contrivance to pre- vent their inequalities ariflng from the different Iengths of the pendulum? in different feaSons of the year, by the effeEts of heat and cold, was firIt thought of, and executed, by WIF. George Graham; and that the application of wires or bars of two metals, which have diffierent degrees of expanfion or contradcion, to prelrent the fame inequalities, was alfo firS thought of by Mr. Graham, and firS executed by Mr. John Harrifon, without ithe leaIt knowlege of what Mr. Graham had done before him.

.

LXXXIX. 24 Lenter from Mr. Heary EeIes, to the Royal Society, coxcerring the CauJ S of Thunder.

Gentlemen, Lifmore, Ireland, fiune 1S, Read Nov. 7, rrHEgreateflctnenofmolEagesha

17s2 1 ing thought it worth the while to inquire, what was the cauSe of thunder; and the world feeming to acquiefce in an hypothefils fub- fcrib'd by fome great tr.odern names, it mull appear prefumptuous in me, to offer you fome thoughts for a t}weory intirely ne^r (at lea-R it z b to me) unlefs I can nlew, that the former hypothefes are ill-

grounded,

[ 524] fore added this contrivance, to adjuI} the lengt};fof the wires; but that, when he had done this, he fio-und inequalities Itill remaining; and therefore juRly concluded, that they arofe from the differexlce in the fxidcion of the different parts of the clockworks oc- cafioned by the differences iIl the fluidity of the oil, fCc.

From what has been lsaid above, it appears, that the improurement of clocks, by a contrivance to pre- vent their inequalities ariflng from the different Iengths of the pendulum? in different feaSons of the year, by the effeEts of heat and cold, was firIt thought of, and executed, by WIF. George Graham; and that the application of wires or bars of two metals, which have diffierent degrees of expanfion or contradcion, to prelrent the fame inequalities, was alfo firS thought of by Mr. Graham, and firS executed by Mr. John Harrifon, without ithe leaIt knowlege of what Mr. Graham had done before him.

.

LXXXIX. 24 Lenter from Mr. Heary EeIes, to the Royal Society, coxcerring the CauJ S of Thunder.

Gentlemen, Lifmore, Ireland, fiune 1S, Read Nov. 7, rrHEgreateflctnenofmolEagesha

17s2 1 ing thought it worth the while to inquire, what was the cauSe of thunder; and the world feeming to acquiefce in an hypothefils fub- fcrib'd by fome great tr.odern names, it mull appear prefumptuous in me, to offer you fome thoughts for a t}weory intirely ne^r (at lea-R it z b to me) unlefs I can nlew, that the former hypothefes are ill-

grounded,

This content downloaded from 193.104.110.34 on Fri, 23 May 2014 23:43:50 PMAll use subject to JSTOR Terms and Conditions