An Account of the Measurement of a Base on Hounslow-Heath. By Major-General William Roy, F.R.S. and...

An Account of the Measurement of a Base on Hounslow-Heath. By Major-General WilliamRoy, F.R.S. and A.S.Author(s): William RoySource: Philosophical Transactions of the Royal Society of London, Vol. 75 (1785), pp. 385-480Published by: The Royal SocietyStable URL: http://www.jstor.org/stable/106767 .

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XXIV An Sccount of the MeaJ>?rement of a Bafe on HO8IflflOW-

Heatb. ty A9jor-GeneralWillialnRoy, F.R.^S! afzdS.s.

Read flom April 2I tO JUlle I6, I785*

I N T R O D U C T I O N.

^ CCIJRATE furveys of a coulltry are utliverfally- ad- :1. X mitted to be works of great plublic utility, as aifording tllefurell founclatioll for almoReverykind of irlternal itnprove-

J

ment it] time of peace, -atld the lJeR means of forming judi c;ous plans of defence againfl: the illvafions of all enemy ill tilne of war3-in which lalE circumRallces their importance

d ' .

ufually becomes the- moR apparent, Hetlc-e it lwappells, that if a coulltry has IlOt aAually beetl furveyed7-or is bu-t little ktlosv2le a f:ate of warfare generally produces the firIt improvetnetlts i its geography: for itl the various mOvemellts of artnies ill the field efpecially if the theatre of war be extenfive, eacll indi- vidual officer lwas repeated opportullit}es of colltributingw accorditlg to his fituatioli, more or lefs tovvards its perZ feEion; and thefe obSerYcations ?veing ultirnately colleEted a map is fent fortll into the world, confiderably improved indeed, but whicll, beirlg Rill defeAive pOilltS out the tleceS1ty of fomethillg mor£ accurate beirlg-ulldertakell when times and circumRances may favour the defign.

The rife and -p-rogrefs of the rebellion-- svlllch broke out ilu the Highlallds of Scotlatld in I y45, alld vwhich was fillally fup-

E e e z preXedX

C 38s 3



386 M or-General RoY's Accsunt of the preIled7 *ty llis 3toya1 HighneIi the late Otake of Cumberlatld at the battle of Culloden in the fbllowing year, cot3vitced Go verllmetlttof svhat illfitlite importallce it wo1uld be to the StateX

. .

that a coutatry fo very inacceble by tiature {hould be tho- roughly explored alld laid Opell,by efl:ablithirlg tnilitary poRs n its iumoA reC&ffits7 ;ttad carr7it}g roads of communicatlon to

sts remotall-pal*ts V§iritI^a ricw to the cornmencement of arrangetnets of this fort, a body of- inAntry was-ellcamped at

Fort Auguttus ill y+7 under the cozrnLnatld of the Iate Lord

BsJaKEsEsX at tilat- tin:w a MaJor*G¢tleral gr at ;whIch camp my nuch reIpeElecI friend the 1clte Lleutetlarat-Gerleral WATSOD{} theil .Deputy Quarter;N4aiRer-Gelleral n No-rth I:>nitatn, was officially employed. This odier, being hianfelf an ellgi- neer) a£tive and indefatigabley a zealou-s -promoter of: every uleful utldeltakiLg, alwd rlae waral arld Ready frietl-d of the inZ duIlrious firLt Otlceiteci the l-dea of makitlg a map o-f the High- lads As afi1i[}a11t Qu$rterMaRer, it fbll to my: lot to beglIl, alwd

afterwards to have a co-rlfiderable-{hare-itlX MtheX execution o-f that map; whicEl beillg utldertaken under the -auipices of the Duke of CErMBERLAND and meant at firR to be confined to tihe tlighlands ouly was neverthelefs at It extetldedsto the Low- 1aM(1S ( and thus made general itl what related to the mainland of Scotlarld the iilatlds (excepting fome leXer ones near the coaR) Ilot having been furveyed.

Altlze/ugll this work, which is Rill in manu;iript,--and in an unfilinled RateX poIleldes conElderable m-erit, atld perfeEtly atl- fwered the purpofe ir which it was originally intellded; yer7 haviIlg been carried on with inIlruments of the common9 or zven it}ferior kindg and the im annualiy allowed for-it being irsadequate to the esecution of Co great a defIgn in the beR manxlerS it is rather to be confldered as a rnagniIScent rllilitary

- + Aetcha



MeaJtXratXctt ff ov BaJu 0Z2 Houzlflow-Heath. 387 fLetch,, than a^very accurate map of a courltry It sYoUld however-, have beell cotnpletd, at d- many of its ianperfbEtiOlls at doubt remedied; but the breakizag out of the war of 1 75S preveilted both, by; irniIhiilg fervice of other killds for thoNe who had been employed UpOll it.

On -the COllClUiiOR of the peace of t7632 it came for the hrR time utlder the corw{ideration of Governmentto make a gelleral f;srvey of the whole inand at the public coR To wards Kle execution of this work whereo-f the direEtioll was to have been cotnmitted to my charget the map o-f Scotlan(l was; to have been made fubServient7 by estetlding the great tri- angles quite to the llorthern- extretnit of 6e illand, atld fillillg them ill Dom the original map. Thus that irnperfid£ work would ha:ve been ef3ReflcRually completed alld the natiotl wouI&- haw reaped the betiNt Qf: suhat hail bcotl already done, al: a

vex;y modemte extra-expences It mrill not be expit4, that I thouldv here attempt to a£1ignX

cauSes efor the long zdelay tilat has: taken piace in carryiilg a work of fo laudable a nature into executiotl: fuffice it to fayX that a p¢nod d twelve years 0 havillg -elapIbd, -litlce the Rheme llad beetl firR prd as a work that could be beR executed in ti¢ Qf pXbUII- zace, without any bthtlg beingdone in it? pwviousfto the nation's butlg-unfortutl.ately itlvolved itl the: ArnericaSn war, it was fufliciently obvious, that peace nzuR be once more rellored} before arly rlew eifortX could be made br that puy. > Ill the mean while, -as I fiill elltertaitled hope; thXat a wvrk which Semed to merit the atNtentioll of the pulzlic v.ou51dX at fotne ;future period, be l;egun,- and, by gradal pers fez vgrances ultima£ely brought to periediotl; therefol4e itl the courlb of rny ordilsary military employmetltsS whereitl the very beI} opp=tunities have offiered of xquilillg a

thorough



$ - lDIajor-Ceizer;,-l Ror s AcozSZ g the tTlorougll kllov1edge of the country, I have - not fiiled to obz felqve) at leaft in a getileral svay fucla fituatiotls as feemod to -lJe tle lveR adapted for the meafuretnetlt of tlle baSs -tlklat -^vould l)e lleceIlaly for tlle forlzat>tl of tlle greatwtriatagles¢ tallul colltweEtitflg ttie different WerieIes of tlaelm togetherX

Tlle pi3ace of wa783 being con-CEuded) atld offlcicll buftlefs 47havitlg detaitled tlle itl or llear tOWIl dtlfil-iozg the;whole of tlla9t fur<luer SI*enrblaced the opportutlity for rny OWI1 private -amuSernetlt to nweafure a bate of 7744.3 iet RaclDfs the fields between the Jew¢s-Llalp, near Marybone and:0 Black-Lane,-

ear R4lncras; as a foundatioll fior a SeI<ies of triarlgl62 carried -oIl at tl-le fame tinze fior detertm-znillg the relative f1tations of .tlle 1no{t rema-rZkable Iteeples, atld otller places,- iniand about -the Capital svieth regard to each other, :altd the Royal ObSerZ watory at C3reenwich*- ;The pritlXcipal dbtEt I l} ad here in view f.(befides tllat it might poIElbly Serve as a hitit to tll-e public,7t for the revival of the twow almoiR forgottell i:cheme-of 1763) svasX to faciltate-the comparifoll-of the obServations, made by -nvthe lovers of aIlrollomy, 0vithin the limits of tlue projeAed -lurvey; Ilamely, Riclmotld and Harrow otl the weLl; and S;llooter's-ESillandWatlRedX on theeaft: and thinking, that a

apers colltainillg tlze refult of thefe trigotlometrical operations, might not prove u1zacceptable to tlle Royal SocietyX I was en gaged in makiIlg the computations for that purpofe, when, very unexpeAedly, I foutld, that all operation of the Iime nature, but much luore irllportant ill its obje& was really in agitatiotl. This I faw would fuperfede, at leaR for the prefetlt, my osartl private obServatiors, and perhaps render thetn wholly uSelefs unleIi it wer;e a5 a matter of tnere curioflty hereafterf to fee hosv fir fuch as depetlded OI1 a ort bafeX gatld: a -ftilall xlzAruXnellt (a quad-rallt of a foot radus) woulsl agree witll

;^ thofe



]deagiretsenz f v- BaJev on Houn-IlosrTkatti<. 389 thoIE founded on a- mucll longer baliX and angles determilled by a large eircular in0rurnentS beitag that propofd, as tlze bei} ;that could be lmade uSes of ln the oreratiot; nON\r tQ l)O

*. .

mentlonec tc

h1 the lze;inniilg of O&obels x783, Comte D>.DMEMns,

the Fre1lch AlubaSadol, tra1lfmitt-cd to Mr. Fos tlleil olle of llis MajeIly's- pritaCipa1. SecRtaries of State a A!emoit o£ M¢ CASSXNI DE THURY9 IN svilich 11e Lers Sortll the great advanff> tage tllat would<4 accrue to aArotlomy? by carryiilg a filFi-tS of tviagles from the neiglibourlioodSof Lolldon to fDoverX there; to lJe coll-neEtedb witll thoWe already executed;i ill France by wvhich combined) operatiolls- the relative fituatzarls of the- tssrca-

.. \ H .

moR fiLmous obServdtories ill Europe, Grectlwlch and Paris7 would NI)e more accurately aScertainedit-han t-hey are at preSent $*

This Metnoir the Secrerary of State by his MajeRyss comX smnnd, talaftnitted to Sir losz2u BANKS, rlle very reEpe&aljle- an--d worthy. PreSidnt of tlle Royal Society; wlio about rlle-- laliddle of Nove£nf;erg sNas pleaSed to commtl;nlcate i-t to mx3g propofing at the fame tiameX tat I- auld on the part of the SOCIetYN charge myfGf witll tte CXCCL1tiOtL of sthe operativ* lSo this propofition I readlily aISented>- on beitlg foon afterwalds aflu^ed, through the proper official c03antlelsX tlant my under> taking it met Withl hsis MAje;)7ss moRgracotls>appro}iatiOt

A generous and bentficent Monarch, wthofe kIlosvIedge a1ad love of. the fcietaces are fufficiently evinced by -tlae protedoah XVhiC11 HE conRatldy ainrds them atad under whofeaufpices they are feen daiiy toflouri¢, footl Iilpplied the flllds:that were jud;ed nec;Cary. Arhat hflis REaJeSy h-as beetl pleaiEl tov

* I CASSIDWIM MeInOir Wi<l th& ARronomer. Royat's -lemarks on wliat ls therein aIledged concerning the uncertainty of the relative fituations of the two tUielzYator1es 7 wal1 be gi:vesa in tlut fctlclgy

pve



39s XlfJJarSe8erai RoY§$ £t¢C§88! ?/ /9

g:ivc fo lil)erall>tS it is our duty to t-nanage wiawh proper alad 19e- (^otnillg frugalityl coIlflRelzt vYitll tlle l)ei} ;zoSoble execution of tlae=lvlfllles to be dotle9 fo asm to make it redound to tte credit of tile Nation ila gelzeral -and of tElib Sociery iJ;} particular.

tlnlae fzpel-ations sntllereof vre al C noW to giVu fotne account, leXgg vlze firI} of the kttld, on atly extetlfive kales ever utl:cler- tElliCLl itl t1tl5 COUlltItys natllrally ellough fub-divides itIclf iLlto r tsvo parts. FirR tlle choice and tneafuretnent of the baIe, xvitll every poffiS]e care atad attentiotlg as the foundatioti of the Etorls; fecolldly tlle difpof1tioll of tlle trialzglesg wherel)y tlle t)Ell^d iS tO L)R COnlle2Cd witll fuch parts oft the coaR of tiliS ifland as are neareI} to the coa;fl of lFrance) and the detertnin-a tion of their atlgles by tneatls of the beR inRrumellt tilat calx l)e olDtaitled fortlle purpofe5 fi*om which the relillt or tcc)tlclllI;on vill be drawn. lt is the firA part only, as a fubjeEl: of itSelf Itffi1ctetltly diRitldc, tilat @sre are now to lay-before tlle Sosciety; it havitlg beerl Judged more advifables to thew that no tieine l}as been lo in tnakiog reaforlable progreIi, tlwan rto defer the account tili the whole operation ffiouldvlBe ultimately com- plxted.

Ckoice of <the Bvfe. Tab. XVI

:TIoulzllow-Heath llaving always appeared to be one of the -XnoA eligible fltuMionsX for alay gerleral purpoSe of the fort ^now under confideratiotl, becauSe of its victinity to the CapEi-tal aJld Royal ObSers7atory at Greenvich, its great extelltX alld the extraordinary levelnefs of its furface without any local ob- :-RruAions svhatever to rerlder the meairernent difiicult; -bew itlg likewiISe colnmodiouflv fituated for atly future operations of a finilar Xature which his hIajelly may pleafe to order to be

este<ded



M{aXUr{AX{St f a B4Me SS HOUI1nONV-HeaX S-9o extended from t-helce ill differelat dietRions, to the more -re mote parts of the i{lalld, it was propofed to SirJOSEPIzI BANESS that the; local circumRatlces Ihould be adualJy exa1nined; So firs at leaIt, as to enable us to form fomeJtidgement7 of the beIt pofition of the lone to be meafured.

T-he -X6th day of Aprilv x784 beilig accordingly fixed olt ir the pxrpoSev -and Mr. CAVENDISH alid Dr. BLA;GDEN accompanyiaig the Prefldellt oll this occafiotl, we l)egin OU1* obServatiota5 at a place called K-ing's Artbollr, at t-he north-weR eXtre1zzItY Of t11e Heath, betzveeI<- CranfOrd-Bridge at1d LOI1g Ird , aNd haViL}g PrOCCeded om ten&e thROUgh thE DarrDW gOrge fOrmeD bY HanWO#th Park >aR+d HAI1WOrtI1-FArZ \vC fi11iFhed at HA1nPtQN POO-I102Se I1ear the fie Ef ]3U<]Y;PArk9 at the fout-heaft extremity, the ttal diRance frDln the fwurvy of Middlefex, lteing upsrards of fiYe miles.

On this it1fipediorl 1t was imlzlediately percetsted, tliat t-he firI:} part of the oSperatiQt itl Qrder tt-o facilitate the meafiwireU ment, vvould beX the S$1eartzg frorm furze-lzuffies and atz-laiilis,, <s liarrour traA along tile heath, as COOn as the gtoul-d -Ihould be fuffi£ielitly dry to wpertnit the l9aCe to beyaccurately traced out Ythereon.

Iiv zracing of the B2fe, at3d clearSizg of he Gro8d. tI^abO X;VIa

Clliefly svith a viesv to the morte efEtcRual execuoti(n of the rork, it -was Judged to be a right meafure to olxtaill atid e£nZ ploy foldiers, irlIlead of coulitry labotirersfs ill <tracing the bafe, clearilg tI le groulicl atid aZRilig itl Dtlle fulfequelt opera-tiotis¢. F>or, at tlle fame tilme that this srasobviou{ly the mofi frugael

etEwod, it tras evidelat, rilat foldiers wt-ould be more attelative > orders thall courltry laboUlrels; and by eticalupiLlg o11 tE<e

X cIJ-. i );SV F f f ipot



39z, M0jor*Gereral RoY''s' A;countE < the

tpot would fiarninl the neceiry centinelsS particularly during tlac xlightX fior guarding fuch paft5 Of tlle apparatus, as; it wav

tore-feen llliavit remain ca}Xtfully--u}touched irl t11¢ Sequent ttl-; terirns of dSiScolltitluillg al<d refil:lming thef work. - Accordilzglye a party of tlle I xth reginleIlt of fioot, conflfiing of a Serjealat,>: corporal alld lo mellX ss7ere ordered to marcll Sotn-Winalfor to Hounnow*Hea-th;, where ahey etlcamped O:I15 the <6-th /of Alay, cloft byt Hans^torth Summ3er-houfe, to which fpot the lueceffary terlts, camp equipageX and e<t-retlching; tools, &c. had been previoufly fint. \ - f

Whatever mig;lat have been the partiicular direAion given to tI<e bafe cotlfidered by its extreluitiesf fioym confulting the E?lan it will eafily Tappears thtat;f;it mufi almraOrs; rleceflilyL^lead through the Ilarrow gorge of the Heath: irtne(l [3y Hansrorth-aS Park alld Harlworth-Farm. The firfi poilat therefore to 15-O} attended to, in tracillg it out} wasy that it: m-it lead through -tllis pafh, wigthout interferitlg with cel-tain fponds) or gravel-pits:*-- full of water, -wkicll are itl it. ThefFe strere eatily avoided by carrying the lille pretty near to TSanworth Sutnmer-houSe; alld ;n direding thef teleiScope from tllthce towarcls the fouth-eaR, xt was accidetltally found, tlaat byq leaving Hampton- Poor-; iloufe a very lit:tle to the wezvards or rigllt, theline would coincide svith a re£narkable high Ipire, feell at the dillance of cleven or turelve miles, and ktlown afterwards to be Baillledv ChurchO As there could not be a lzetter flaated, or tnore cvnfpicuous ol)jeEt tllan this, there-fiore0Sthe firA or-fouth-ea feAion of the- bafe, comprchended betwesen the Sum-mer-houSev -alld tlle allgle of tlle finall feld adjoitailag to Hampton Poor- horlfe, was itnmediately dired:ted upon it ,- alld the foldiers were the fame day fet: to work to clear! the tra&, -which, at- a meZ slilltlly vas maele fiom tsro to three yards in breadth. Thi$:^

- . opexa2fols



MeaJvretnen of 7 a BaJve on Aouflilow-SIeatho : 3gS operation colltinued eight or tengdays, owing to the lossrer part of the heath, lJetweeol ! WolSey-River and the Poor*llouCes being encumbered with brulh-wood,

Whe-n the c:lsaring of the firR fed;tioll was completedg tile feconds colnprehended betsseell fhe Summer-houSe and the greae road leadillg frorn Staines to London was traced QUt ill the fiollowing rnaIlner Otale o£ the pyramidal l)ellstents (sYhereof tsvo Elad beell provided, orie::of twenty five, aad ttle other of fifteell feet ill hetght)- beillg placed at the Ratloll rwear the Summer-llouSe, camp colours vere then arraugeel ft^om di-Rance to diCarlse; ro as to be inp a line with tile bell-tent atld Banlled fpire. ;:Ils lilzei rn-annerj the-thirad liEtion eomprehended be tween the Staitles Road alzd King's ArlsourS was traced out,

This firit tracillg of the bafe was dotle by tnealls of a cotui motl telefcope helDd iII the halld ollly tlaut no time tnight b¢ IoR in employing the foldiers to fmoorl:l the tradt which was to

be mealilred; becau-lE the tranfltfinftrumetat: (myl o-wn) p-ro perty for which a portable lland had beetl fiol fome tirne- pre- paring) was -not yet ready to be applied, as it asftermrards waS5

snn trACilig OUt - the -baff-e: more accurately The camp R-ill remained where it was origlnally pitcheds

at the algle of Hanworth-ParkX this being a very collvellieI3t O .

p()ltiOns with regard to the firR atld.fecond feAiotls; but being -too remote from the tEli:rd, that tirne might not be IQ0:, alld tEle men unneceflarily fatigued in marching backwards alk forwards ;- thereforeS otle;half of the party, under the colBma^Ild

of the GOrpOrals WE15 detached to the northward, and qtlartorxd itl the Ilegllbouriilg villag;es, to clear tile tllird fed;onX whi}e

, .

t-the ferjearat, witIa tbe remaitlder, were occupied in ioothita-g t4he i:ecolad. C)Nsr;lg to the extraordinary wetutfs of tlie a fon, this operwtioIl required more time thanlhad beerl at firft

F f f X imagitlecl9



39+ jorGr?ZerNl RoY+s JccsXt af -the

i2lagitlCd IlOt having beell entirely fiiiffiedSbefore;the firA xveel<: of }5ulyo NYe tha]l-tllerefiore leave it going o1]9<and-iz the lllean time proceed; to defcribe the iLlIlruments that were i tlbfcquclutly nzadc life of ixl tlle firR-alld fecotld meafure- m.entse.

Steel Oasin, Tab. WIT.

Olle- of the fir^I} illfll^utneIlts, whith thit able artiR R-AMSDeN had orders tc) prepsare, was- a Ree} ch-aill,- one hulw dred feet s;X1 letagth, tIae-; b:flt that he could m;alieJ Not t:hat iiz was itltetlded7 tlor; could it Le filppceSed, that xve IhoUld abSo iutely abide by t!-le refult that tht-s- clla;t} ffiould-furnifh u with, for tohe lerug-th of tlle bafe; bttt it was hoped, that aIl iIlt-Mmellt<Of iiSefOft mit i mais which would meafure-- diflatlces much more-> accurate47 than- at3y tllilzg af that kind had- ever dotle beforeot and t was- cotlfitdered as an objeEt of iome conGequence, to etldeavour to fimpliR alld rellder as eafy as poilble, the meafiuremel}t of bafes 8il future-* ato operation which, hitherto, fias al svaysfi b-een fot1n-d to 5e-tt&OU$- alld

7troublebme, to svhKh we may now furtller add7 uncertaiI<A likewife, whetl done with rods of deal>+ asA will a;prpear from theX account>liereaofter to be givel;

The conRruRion of the chain, whtc-h is on die prin-ciples of - iat of: a;watch, will be utlderRood frotn the repreferltation of forne of; its chief parts-> to tE1e fuli; {ize,. n tab.: XMDII. X wrhere rlae firR, or z;ero--elld litak; is {hewrl botla in planbatld el-evatiol< Ril th-e Rate iSn wht£tl it wa-s origtnallyt applied to X meafuremeiwt pll the furfa¢e of the grounal. :Each lnk colwfiIls of three prilacipal part$ lmelyfe a lotlg plate; two Ihort- oneS half the tlaicknefs of tlle formory with circlllar holes n;ear the

3 cL£rtmities



MeaJ^reenrxt of a I3t7J*e on TIounIlovv*Heath 395 extremities of each; and tsvo crl{}-iVeel pitls (r axes, fuited to the dXiaxBeters of the llolex, nvllich ferve to coltledt- the adjoill ilag liwlks eogetller. tI}}e holes itl the nlort plates are -nlade rougE.j. or jagged saith a LSle; rO that wh>1l ttley laave ernbraced: the ends of two adjollling lollg oaees) alldwtlle piaas have pafled tllrough all the koles, itl rivettillg their estremities, tlleyt are made perfeAly faft, and aJ it were ullited to the ffiort plates; while the emblaced etlds of the lollg ones turn £ioeely rouncl ota tlEle middle part of the pins

At every tenth litlk the jOillt) jufl: IlQBr deScribed, has a pofitioil ata rigElt^-angleXs- to the torluer; that is tQ {:ay the ilzolXt

plates- l.ie il.ere horizontallv, and the- pins laAitlg- tilrough tIzem llarld verecaliyY 'rlluss there beillg in the wholet chail- two 5aundred cXa-*fteel E)insj one hualdred- and eigllnty lie hori zontally ;-f and ti\<ent itlcludilzg rlleu two by svhich the Ilallv dles are attacl-led, fiatd verticalliye. Thefe crofsjoitats>whi were chiefly intetwdedl thalt-tEle chaillatnight foldJup ill a ftnaller £ompafs by retllrning UpOIl itfelf a-t every tent}l-linl(, are

llkesvife uNeful in preSellting a horizontalt furfaceS to svhicl fwnall circular pieces of 1)rafs are fcrewed;^ ttith - figuress J : 2s. 3 &c. to 9,. ertagraved oil them, detloting the decimal pEll4tS of the length. T}-lus the middle croEs joint, or that which feparates tlle soth froln the S:IIt link iS IhewaP itl the Plate sv3lh the figure S UpOtl it

The chain, ill its fi rll conErudcion (ir we- are- tlow t pOillt

out fome alteratviotls that were atliertrards made in it), was olle huladred fieet iIl Iellgth, including the two brafs haradles; in the extremity of each of which there Was\a femiwctrcular hole, of the falue (liameter with the IVeel arro-ws fuccelEJely fixed irl theground, atld Nerving to keep the accoullt of tlle nu-mber of CtlElillS) when applIed to colnmotl meafureuzetlt. Ill this its

firI}



BgX Mayor-Gemeral RoYss Xccot i?f the: firIt Lmode of application it was foon dlfcoverez3 as; we fllalt have OCCa6QN to tnention hewaRer how 0-admirably -th-e chain performed; a-lld that, with folne fartller precautiollsS a Rill ;eater degme of exaElaefs migh:t be atrained, ly fupp<3rtiag it o1-1 Ilands, or evetl on pIatlks, lald Oi2, or b-ut :little ranoved firoin the cotnmoll filrfice of the earth. For this purpoIte, t]<e two eald-litlks we--re altered7 -each being tow made equal to olle foot} exclufive of the hatlelles. tBy teferring to tab XVII. the nature of tllts- aIteration will 1)e- eaflly conc@ived. It cottlfilfied irl fcrewitlg to : tho; utldesr flde of the handles very near the jOintS, two- Satheredged pieces of brafs $; the -one denotitlg zero and the-other IOO feet. Over tile dart at the firR, a plummet zvitll a fine filver warire beillg ftlfpended that wires by a very Iimple apparatus, hereafir tQ be delicribed- may be brought :accurately to coitlcide 0X=vith -any point -wh-atever of commencelment: atltl at the fbcotldt a fila: line with a ktlife, or otller Sharp illItrument btttlg d-rawn on a piece o-f card placed there for the purpofe, and cha1aged as oftetl as need-ful; or as svas llketstife pra£ti-fed, a-tldE fouwtld to anfwer bettex - a lin-e otl a Inoveal)Ic {lide of braXt attached to tla-e top of the Ratad or-plallkX beitlg-brought to coillci(le with th-e Sa- ther-eclgey atld0thelllfiRelled underneath; the-extrefmity-of tl¢ IOO feet is re-adily aCcertaitled: and tilUS the ulearul etment

may be collti2;luedX0ll with great accuracy to any cliCaIlce at gpleafore

That tlae cllaiXnS iI} tiliS its aItered Rate mcay Rill b;e advall tgeouny applied to orelilwary meafuremellt on the filrface of thezearth, tilepieces alJove deiScribed havillg Ready pinss and being fiftetled with fcrewsS caIl; be eafily remaver3 atld otllhrsS

* T-tty-were oiivnally of braIia but are now of ACeI} thatthe ed>¢es by being hrder Inight rnu -lefs # rii of-- be dama;ged.

exaXtly



M@retngn/-ef a BvDfe on Hounnow-Heath. p7x exaRly of the; fi-llle length;>- fulzIlituted ill thei-r Read-, witl- fcmi-circulalo holes; (as- repreferlted in the lvlate by dotted lmes ntalX the joitlt of the lzalldle) to receive the Reel arrowS then to- be:- made ufe of i< the mFatluer already mentione-dt

Thixs moR ex.cellent chai-tl feelils not-to: have fuffibred any perceptible txteaI;on from the uSe that has hitherto -beelu made af -it. St is fo accuratly conRru&ed, that when firetchedsout on the groutld, asl ill commoll uSeg fall the lotlg plates :}yitlg v.ertically or edge-;Nvife, if a pe-rfon,^ laying hold of either elld witla botll hallds, gives it a flip or jerk, the xnotion is, ill a iw fccolld--sy colninullicated tQ. t1At other etlds in:a beautisful vertical ferpulti;ne litlt; whe- the perfon, Ilolding that handleX

. .

receivestaifusdden Ihock, by the weight of the chain- pullillg laim forcibly. The chain weighs about- eighteetl 30utlds,. aI1(1 wheIl folded up is eaf1ly contained in a deal box, about four teeIl iilches 1ol3g, eight inches} broad> and the fame in depthPE

Deal RadsO TalJOX XVIII.

The I5ais whicll have hit-<-herto been meaf-uted in- difirffllt c0v3ltries, svith the greateR appearalace of care and exadliefi, have all, or for- the mo?c part bec1w dorle svi-th deal rods of Oile

. . .

kirlld or other, -svhtSe letlgthsV lJeirlg originally aCcertaitled by meanS of fionle rnetal Itandarel, were. in the ful)Sequellt applications of them7 correSd by thefameRandard. EXavirlg thus }lad r maIly plecedents> ferving as exGmplessto guide t1S in our choice, it ssras natural oenough that we {hould purfue- the faxne method in the meafiurement toSlDe executed on Hounflow Heath; takillgs however, all imaginable care, that our rods flzould lJe rnade of the verqT beR materials that could lJe prt

cwured:



398 MajorGextral RoY'0s Account of Jhe cured; wtth this irther premutaon, that ly trufl]l^g-thems they SllQuld be rendered perfedly inRexible, a circumRatlce llOt

bebre attended to As fome difficulty had been found itl procurlng well-Seafoned

Pine wood of fufficient lellgth, altl ?erfEEtly free Som knotsj for the inteIlded purpoWe; therefore Sir JOSEPS BANKS had- earlyapplxed to Cthe Admiralty br ail;Rance in this -refpeflC; alld fbrthwith obtained an order to be furnilhed with what we might havesccafiow br, fioSu his M<3eIly's yardWat Deptfbrd where an old New-England maR, and alSo one d Riga wood, were fipeedily cut up fi)r our tSe.

Nessr-EIlglatldWwhlte Pille is lighter lefi liable to warp atld lefs afl:eEted by mollture than ELsga red wood. 13ut the Net- Ea)gland mafty whell it catz3e to be verySminutely examieds was found to be^-too much woutlded by &ot-holes in fome parts? or too mXuch decayed or knotty in- others, to affbrd us a fufE- ciency. Tllis l¢irug the- cafe we had recourIE to the Riga wood, whicll was illied esttemely fmootEl atld -beautifil; alld b perfE&ly Araight-grainedt that a fibre of it, whell lifEed up} nigllt 1)e dranvn, like a thread almoft Som olle ttld to the

-s)t, ler.

It had leen ill colltemplations to make the rods of tsventy- five or thirty fEet ill letlgtll; a-tld otle of the itlller dimellfiolls was a&ually cotlflruAed: but tllis beitlg fbuIld to be rattler too ellwieldy, it was judged be{t {to colltetlt ouriSelves svitll tlaoSe.of alsout twenty fEet.

;)iX«erel1t OPiR;ionS haVe boell el1tertailRed VV;th rtgArd tO tE1eSbe{} mOde Of aPPIYiDg rOK1S in [neairEn1eNt; IBl1AC COI)tUl1ding tlLaT COI1tA&SS Or tt Of bUttillg the elLd Of OI1O rOD ag(Ri[tA Cl)C eIXd Of 11C OThCR,- iS The bC0; ;-X \hiXe Ot1zUrS (AT;tI1 mO1^C PrOD;1biTiFS cf

l;)eil.g



ga,remett o, a M*e Ot2 f lounnow-Heath. : belug rigllt) are of opinion tllat the-adjufEment ltyi the coin- cide1wces of li1les {hould have the pleferetlce. The fi-rR is ur doubtedly the moR exped jitious method; but Weems at the fime time Sto be Xliable to tlais very o:bjeflclellable circum0alzee, that tlle probable trrors fa11 all one wtayo wh-ereas, itl the fecolld tneZ t1wod, although by £ir the lnoft ztediq-us, the errors of coinciw dexqce fallitlg fetnetilues on one ficle, alld fornetimes-olw-tha other, they cotnpenfate fort or deRroy, each other; gld therefore no error is coxnmitted.

With tlle view of fatlsfyitlg laoth ?art-tess and ill order to pU£ tlle matter, if poEilule, out of doul3t, it was judBed proper to con:Rrudt the rods ilu fuch a manr}er: as to admit of both me- thods lJeing triedy tllat we tnight adhere to that wllich {llould W found by experience to be the beIt.

Three meafuritzg rods were accordingly ordered to be made,, and alfo a Italldard rod, with which the former svere ffrom time to time to lbe compared, Their general collAruAion will be better: conceived fFom tlle plan alld elevatiotl, and otller reprefentatiotls of theil- principal part$, in tab. XVllI. tllan by any defcription, however part- cular, cotlveyed ill words. lt will: be fudiciet}t to Idy, tit:; tEle Relus of the tllree meafiurillg rods are each twexity fieel:

three i2-lches in length, reckenitlg Dom the extremities of the bell-metal tippings ; very near tsve itlches deep ; altd about X i -lNCt1 broad. BcitE truXcd laterally alld vertically, they are thereby r elldered perfeEtly, or at leafE- as to xCetISey -il<flexible>. The lEan dard rod could o;zly be trulSed lcstetally s and it isJuRly wpre fzllted by the plaxi of tlle otller rods, excepting tllat its ftem xs fornethig firolager, aIad that it has two or t},ree i2lclles at eactl ctld of ext-a-lellgtia, :twhe reafons for whichSdiffere-ce-s svifll appear Ilereafter

YoL. lgXX\re 7 g $ By



,oo A!ajorGexeral Ptots Accoant of tbe 0>

:13y refelrillg to the Platt ilt *vill 1)e obierved t;hat two 0nDar tO\M pieces of lvolyX eacEl faRetzed sxithf t:vro ffrnall {crews, am

iEllIzid into tile upper fu;rfice of the rods xvithin one t-tlC; allF a half of the extremiti(es of the tippings.\ Thefe eivory pieces r;eceived the fiile black lines cut iato t11en when the lelagths of twhe rods were laid ofE, in tlle matlner hereafter to lJe- mentionedw andi accurately dereriniIled the inter£2ed ate diRaLace of zo feet. o-r 240 ilaches the meafure to: be; iifdd ill the application by coillcidences:- svllereas, in that by co1wtads, the ipace com-- prehe1wdYed between tlae exLrenities of the preieAing lips of- the tippigsS is z43 itw£hes<. 0 - \ - 0

Irnnaedintely lehlnd+-each ivory piece, a cavity ts formed un dei4neath n the miiddle of the:i'setn. This receives a brafs wheelv ahbout tigh-ttenths ;of atl inch i-tl d-:tarneter, whofe axis tprns-re;the fot41t of a braiifs fpring, five ttlches longg fafietsed by a fcrew to the -unirX irEace>-Xpt -beforeXtEye is atf&t*

Thefe fprin.gs are o-l-s:ly of fuch firenzg!th as tQ permit the wheels X be forced up into rlle/cavt?ties- by-$- the weight- of thesrod>. which? in; its adjufl:ed flcat:e,i al;ways 3reRs entirely on:the ir-- faces of ie two: -fiands that ffiappus t- its: extremattes*> But- wheIa the rod l5 t0 be raifid-from cth-ands, the] the- mille;& h-ded fcresrs,- -pro3e&}wg-al3-ove th:e upperslitEacey Xd aMiag over the middle of :the fForlgs, -beitlg brought to-: a&> -the wheels are thereby preXeF downwards, alld tec;ti:vd the0tfibllLi- vvfeeght of the rods tshich 15 -then > tffiiy-- moted- backwardss or- fornvards to i-ts. tr-ue potion, eitiro:S cortad: oc co-incidetare; ;- - The c:rof>fieet placed about 32 itwch0es :So:rn-:the<nends of the

rods, and I - inchf frotu tEat itaSertson of fthe trufEla;-gsS are each:- - about nille inclleVs lotg X t - broad; alld tlearly all inch ln depth9 }lAVil]g their losver furEaces - level: tith that of the Rem. By

% .. E - .- f ; f mesaIls



-- llIffi?retnen! of a Xafa o-n Houlw{low-IIcarlR; 4Ov

mealls of thefe, the rods are tlOt o£<1y kept tnore Ileady oola *lae falldss again{te tile cotnmoD adtioIl of tlae svilad upon t7ae truS fitlgs:; I>ut.tlley likewife ferve-as hol7:ds fiolo the vel^tical atad lao*i zolltxal; braIi clalups- whereby vlle reods are macle fii{t to tlze fialldS on Otlt fiden or otherX and itl both -tnotles of applicati ols t-olltaashand cc3incidences; as lvill; l?e -more;-silly exlXplaifl-;4 ereafteors -iTl ciefcribiilg tile tops o{5 tlze {tallTls.

Brays Staxdard Scalu, f7gd Serhod f Aazzifug * tke lergfb3 oyr fZ>e - Deal Redr.

At the fale of tbe itlfiruments of tlle late iIlgenious OptiCidll

Mr JAMXS SHORT, I puirchaCed a fillely divided braSs fcales of the lerlgth of 42 itlulles, vvith a VERNIER s diviEloll of los at one endX atld one of stt at tIle others svherel)y the IOOOtH part of atl inch is very perceptible. It was origitlally the property of the late Mr GRAHAM the celebrated Watch-m-aker; has the tlame of JONATHAN SISSON ellgraVed UpOIl lt; but is known to have beels dia7ided by the late Mr. BIRD, ho the worked with SISSON.

It is fufflciently well known to this Society tihat their lzraf& Randard ffcale, about 42 illches- longX whicllv contatils otl it

the leIlgth of the fEandard yard from the Tower, that from the Exchequer7 and alSo the French half-toife together with the duplicate of the faid fcale fent to Parls for the uSe of tlle Royal Academy of ScieIzces, were botll made ly Mr. JONAX

THAN SISSON, undel Mr. GRAHAM2S i[n-anediaCe direAiO11¢ Now, although there -feemed to be every reafon to fuppoSe,

. . \

that the fcale at preSclat in my poSeIEloxl, origS<allv Mr Gasw Ggg; z ; -XAz44s



4Ot Major^CerAZ s3Yts a4ccoBnt ff t , . M

HAM'2S propertys would; corref>nd with thtSe above-mention whi-ch he had bwn dizreded by the Royal Socicys withi fo much care and patnss to Fovide; yet that xxothing of this foR g}tt remaza doubtful, it was judged right iti Sttling the ibSolute lexlgth orf the baSe, svhich } meaired near Lolldoa- itIl 1 78s, as has beeIl tnentioned in dle >Xtrodu&l0n to this Paper, that thetwo fcaTes ox}ld*he adually compa-xeL LIav illg accordingly oStamed an order fiom the Prefidellt, for adt mi«lOIl -illtO iet S-ozety's- Apartmellts I went there in the- aherIloozl3 qf the t>3tth of Auguf}, and latd ith iales takea out of their cafes ow the table of the meetingroom, w;th thermometers alon-tide of them, tilat they might acquire the iTalne tetaperature. On theX forenoon of the tsth of Au guR the col-n.pari{btl was madeX with-tlae atElItance of Mre RAMSDEN, XVhOf for that purpofe, carried -along with him his curious beam-compaSesv zvilofe mlcronlerer-fc-resr ffiews: very perceptibly a motioll of 5rtooth part of aXn illc1l. Thu:s tllc extent of three feetS being carefLilly talien -froln the ; Society's- ilatldar(l, atld applied to my Scale, it xvas foulld to reach exaftly to 36 ttnchesX the temperature btlg 6}5°. Iil like marlllel-, tifie bearnwcompafles beillg a.pplied to the Iengh:i-;of the Exchequer yardl the extent was I]QVS fOtlIl* by the microllzeter to over reacTl that yard by TQ6;,9<otl or tlearly X<,<Xth pa1^ts of as t- 1 I

@1C WA.

Havillg thus IheWIl ttiat mv fcaie is accuratety of tlae farne

ellgtla svitll ttlc Society's {tallclardv -it remaills to poiJaVt out the ufie t}lat tras made of it) for atcertaining the lel-gths- of tllc dveal rods7 il<tetlded for the operatiow on HounllovrzESeath. - 1fl tXle firA placeX sP9Ir. }tAMSDEN prepared a beam compafis iS 5.giCllt tO ts^e iI} tsiteIlty Ret truSed iJlall refpech ltke the

smea



Mfurement of a Ba/^e on YIoutu;Ilos:t-Heath. > +o3 nreafurillg rods, tbut fomethillg deeperX an-d fitted as fufual with proper points atld micrometer. Thte Randard rod being now cotl£truEted was laid ox1 the Iho-pZboard, llrongly fratned i1 the purpofes aRel nearly level. To e fide of ;t, at -the dilRance of about twenty feet two inches from center to 6enter, tAro

lEreng I>ell-metal £o¢ks were firmly fere>red. T;e coclz weire about 4 iliches i^ letlgth three-eighths in tllickllefh md rafe aSove tlle fl:e2n llearly tsvo inchgs? -zfio as to be on the fame plane vith the furface of the meafuring rods, whea placed upon it.

A large plaak, £;Wt fi the NesvEtlglalld fma0, uFwards of

tlllarty feet long. llielle or ten inches;bread, and about three inches thick. I}eillg fet edge-wife il. thse fame room,- on part of the fiallpds now ready for the operatiell,. was, 1z that pofitiolls pla-lbed perfeeely fmooth alwd firalghtt : As filve-r wirez beillg thea- llretched very tight, alollg thse middle of tlle plank, from one e11E1 to the other, fix :lisce<$- s3f S3rty inc}les each were nzarked off 13y the fide of the wire, at which points feve2rl braSs pinss alsout olle-teutll of atl illch in: diameterS were drl>vell bllto the ss-o0d)and their tops polifhed with the ine. D.urn.g the whole of this operationz, alwd tllat lrhi*ch foliowred, the tllervnometerl Sying by the fide c3f:; the l)rafsffcale, coiltitlued Iteadfily at or rery xlear 63°*

.

A fizle dot being now nade OI1 o1le-of the extreme pins, anc}; thefilver wire lxillg Ilretelled over the dot,- az3d as near as poLZ iilJle <3ver th;e middle of the other pilzW itl which l3ofi1tion it was made: fd; the extent=of brty i.ncheS tak-en with the vltmoit care from the bloafs fcCll¢ sYas tTlew Inarkedl o0; by pla¢ing otle poitlt of the beam-conapafles itl tlle- dot,- alld with t1-1e other deSctibil}g- a ffiort fant arc fon the Iillrficc of :tl-le feZ

coniIi



; 4 4 5 Ki R Cese rf? l g o Y S /¢¢ lV ! f t.7:

cotad pitlto - flNl-e^betm beRllg thetl removed,;ataxdtotwe pOiltt

.zlaced tw:tiweyiwterfeSion bE-the atc and wlres -with t}we othet- poi£lt a <det >wasE \ ma4e ;Oil tTle \: tl:tird pit;lx - iztl<-der - ---tiat awiddlei of rlle wireX tUpol} tlwis-dor,:asâCetlte- aEaitwt are was0Xextv 2dekrit3ed oil tlae fame p;Xl whelC tlle: firR I-wad 1JO-@A- tftCe. - ih

tthiR lu<(1llt3er ttle fil: tinAtS irty ;1athes Were inalJked oS, -alter ilately svith dots ;and ;arcs -; a^ i>ethod - fourid hy Mr 0RA M5DENt till hi0s 13r1&ice, to be siolê acctlratX thall when tlots only are

s h - P uaût u-te o^t Tlle exaA leiigth of twellty fiety -thus obtazzed, was tlest

talien lJetweell the pointsi offthe; l-otag beam-compalSes, a1zd trarlsferrefdfta -tI-le tops of tlwe :t [)ell-nietal cocks, ̂ placed:;, as has : been already; - mentioned, - oh -tlie- Xf- c1e d kthe 0Randard; t rod, iIl

fuc}< matlner as to leave tnore thatl one incllZand a half of the .Xid4- cocks btond or: mthout :the - lines ̂ de£Roting the extellt of tlle twetlty St. tThis being dolle, the tneaiMirirlg rods were ;fucceIEvely placed on-tthe; fl;an7&iard,- aM thear fides applying ocloSe to- the cocks, the difEance fof twenty fEct was readily stransferred from them to the illla1d ivory pie¢es, on which fille liefs were afferta.rds BG\lt7 by Xmarks acourately made for that .purpofe.

With repril to-the adJuR1netl-t of -theilips of the be11-metal ttgippingS, which;extelld exaaly olle inch and a half beyond tEle -ivory litless fo as to tnake the total letagth Of Fthe tod z43 inches, it is to be olServe(l, that they termi1r;ate ill flat curves of 32 iktucl:es-¢ radius?: paffilg throug:t-l the:inch and half points lao which-t}aey v%Jere cautiouily ground dosvxl, that at firR they mig-ht -ratller exceed thatl be defe0;iv-e in lellgth. Any two of the rods, liying itl the ;fame plane, alld alfo in the famx :firaight lille,--being brought into contad with eacll other; 1f

of



rencext of a BaJ!m>EIounnow-Heath. ! i!-the truRe legth, Hthe iace itl ;th-at} poflti-!otlx cotmrpeS i11id ktwee2l thes two nlitle$ - tht ;fuual4*ivoyrys piezv s*szmuR be aadly thleFe stlchefs. For the purqoStof t:his 0adj0:-ll0;t@>ntb-t

astetlt d three- inches was therefoe taKg a- Som- the bra:li JScale and -cat ;uspon ;-the:zfii of '5 a dewhed;0pietce of:ivory;0-whicl bCillg readily > ap plied - to < - t}led > wafi& X iXermed-iate 4?ace* - th; fa was grad:ualJy reduted; w-grirlding; ;+thQ lipss qXlly;- till it exadsly correfipotlded trit¢ht - that ukenv 4fionls tihe fcale

T1w2 three ro ate tlu:bere54 by atcypher OI1 Xtlle -furfice of

the metal at each>ex<d> +X*2:; s3:4 - 5.6, -alld- that being tllse order itt which they .Xvere fto EtXe appliedRlt} -g4prl pefiferen£;--{4 it

was. ll5kewifE the 03nder-.t<:which tht xwer.-e.+-gdjl;i.5h. dft*tht.is.to £h the rod 1.2..-- was ;.adjufidd ;with . .4>. .a;fid w.SthX . g.6 -§ alld the rod-3..4.was,.in: likeman.l.leS.e.acuuIledQwwit.h . ;Z and>5.6.

One o£ thefe -deal0.rods.v.theI8.. fiiZnilieds;....was- f.oun..&. to weigh tw. tyw four poutads. They Vwere .iM¢iwdW totbe £ootaind in two cheIts, . olletlatV.atld--th.e ;othDet . -iRnall¢ ---t tFhe laE -- cheR9 which is about 3 feet deep,.ma.y be cal1-ed a double.ot.le, becauSe i.thas-txvo lids that lift quite ofR which, in turlait}g. upElde. down become al.ternately tops and lsottomS ha.ving.;.l)etween them , - but zmuch - nearer i to: sthe .o.t}e .-tha1l. tlie other: . a -- bottotrs that is commo.-tl to .bothD The {lhallow Ilde.holuls ths Ratlcl;}rd rod ;- alld the-ot:her, two of theE nietairitl-g rod§7; -NvhSich laI} is rende-red pradicable by havillg otle of the Iide brace.s ;of.each; fixed only-.withhScrews fo S5 t0-be- xmoved and4.riepldoedf af

pleaftare. T*hlls- one (3f the rods-; bei1>g -l-aid m tit- pia&&- the other is-put over it n ala invertdd pofition, .--and--1>0t1.l5thavait t13e- p.roper fiRenfitlg.s: ;to -keep theml it} their. pofitioia.s trlae lid is thetl put otl, atld fixed byRrews. -?Fhe chefl:-;ltting--n-oSw turLled upSdet.:ddwtsX a-.dh the othe.r0. lid ^et.<lov-d>¢-- tIa:e. hndaerd is

therelv



Xo6 MiorGeal RoYss Acco2XX +0theD thEreby diScovered reflillg --otl the common lottom, - Swhi$--- Ilas bsuds ilWaid acroti xt for the purpoWe, a few inches bebw what has:0tlow;biecomeD the irfice nof- -the -cheIt. lt was- nece{: firy -tha-t the lEandard -Should -reR thus hlgh- both -th-at- the; light might come fi:tely upon it, atld that, beilig eI;Ipported by the deep fides of the cheRs it might be- preYe£i-ted- fitom twb illg, forX it w11 be mmembered that it--is oidy- -truffEd- laterally.- By- lntans of a iall brafs ItrXing - fi-xed to feach; end 0 0of tile fl:hndard, a fine-filk thVread, as l)eltlg lefs lial)le to accident than filnter wtre, is retchedralong its fiem, whichfby Iinall wedges prepared for- t:he ptlrpolis and {lipped in lzetween it andithe batlds an: whith it f@0S} iS ElWvS brought into the fame pofi tisla. This fbeing done0* the:-fill *thrd-- it turn;ed ofl; r- :a5 to

perlnit the meafuritlg rouls to le laid oal t1at ftandard for:co-m- pariGon. Witll regarcl to--the ftualler cheft fuch a one was adEually made, arld fe-nt- Elowil to tlle hathe-towa-rds: the ;XUlaS

of tlle operation- strith the deal r-ods ; lbut from fonle rxwiIlake sa

itsEdimeraiRops- - lt would aot ad-n-it tht>third rod^. -

Nfandsfat-te-ll-ea*/rittg RoJsX> .rTab>-xUII-."-atld S=*.

Frorn the extraordttwary leveltlefs: of HounIlosv-Heath, 6e; uScent fFom the fouth-eaR-tosvards the Ilortll-Xveil--beitlg lttle more than olle Sot Ditl a thou: ad ill tlle diRallce of five miles, it was eafily feell, tlwat tlle cotnputed leafe-lin-e; or tahat aAually; Frmil g a curve paral}el toStlle furfice of the sfea, -at that laeight above it, would fill fo little thort of tlle llypotiletlufil diflallce, meafured oll or parallel to the furfice of the Heath as- fcllcely to deIerve noticeS i-lad it IlOt been tSaought llec-effirJr to

2 ,{11esv



Mea8Sreenen! of a Bayte on Hounflow*He:th. 40y flew, how much one etld of the bafe was really higller than the other, and to convinw the world, that itl aIl operation of this fort,-where -fo^much ac-curacy was exped:ted9 no pains mTere fpared, nor-the moft trivlal eircumRallces neglededO

Fw-om the trouble atld uncexaitqty attendirlg the frequent uSe -Tof plummetsS efpecially in windy weather illIlead of mea furing -level or bafe lines, as has hitherto-b-een cuRomary (itl which caSe it would h-ave beerl rleceSary to make uSe of the plummet, ortfome fuch contrivarwce at every ftep of afcent or defcent3 it was judged to be a better me-thod to- meafure hye potheIluSesS and, having obtaitledthe relat-lve heights of;the Rations by the accurate application of the telefcopic fpiritZ level, tO COlllpUtO the baKe litles. Thus it was propofed, that the leagthK of tlle bafe on Hounnow-Heath Ih:ould be obtained by meafuriIig a line through the airS drawn parallel to the common furface from ilatioo to Ilatiotls in equal diRances -of -oo yards or 6ooXXfeet each as repreSellted ill the-figure at -the top of tab. XVIII. - 0

--lFor this purpoSe, tsvo kinds -of llands were ufieil; one whofe height was lExed, io be: placed at -the begitanillg and elld of cach Qzoo -yards; alld the otllersX whoWe heights svele movea ble, that their furfagceKs tnight be larought more eafily to COill-

-cide with vthe l;tle p-az-rlg throEh the air from {3n-e fixed Rand to the other. The Exed Rands in thelr Erft liate, repre -fetlted by that towards the left-hatld in the plate for -the deal rodsX were only tWdo-ieet lieven lncheu in height; bu--t ssrheIl the {glafs tods were aftetw-ards uSed, they h-ad atl additiolaal piece of ten ill-cl<es faRened to the top (as in the leRhand Rand of tab. XIX.) which made theirS total height above ttle Heatil7 including the platform ot1 which th@y 00d3 three feet alld a half. They are tripods of white dealX whofe legs extetld alsout

Ve LXXV H h 1a thre-e



r+°S Major-General RoY9s Account of the tlnree feet from each other, and being l;)raced diagonally: are mortoifed at top itltO circles of the fame fort of wood. Over tTlis circle, a fq-uare table of about I 1 I it<ches is fixed, com- - pofed vf oak, aIld mahogany at top; but both talien together do llot exceed 1 4 inch in thicklleEs.

--Jrhe nature of the moveable llallds, whereof there were at laR IlO fesver than feventeela provided, will be canlprehended froin the reprefentatioils of them towards the right-harld in tab XVIII. alld-XIX. Tlleir general collfiruEtion ill what regards the part of them which is fixedS difEers not from that of the orlaers} exceptirlg that they were of dlfferent heights, froln two feet to about two fieet eight inches? fo as better to w

fuit the irregularities of the ground where it might be necef fary to place them. Ill the middle of each of thefe, atlM hexa- gonal wooden pipe defcendsS from the top to uril;hin two or three illches of the bottomX where it is joined by a brace reachig from each leg This pipe rtceives the common cheefe prefs wooderl fcrew (havitlg three fides fcrewed a three plane), to the top of which the fquare table is fattached It is embraced by the circular nut or witlch with four handles whereby the table is elevated or depreXed at pleafure ; and beillg brought to its proper height, is there made perfeEtly faft lyy Ilzeans of the flat-laeaded iron fcrewS which palElng througll olae of the legsX prefles-an iron plate, fixed in the inflde o£ ti pipeX ctgainil one of the plane fi.des of the fcrew

In delcribilwS, tlae deal todss there has already lJeela occaI;on to

nzake lmention of the vertical atld horizolltal clalnpsvwherebythe croSsfeer are fafietlecl to the table on the top of the ITand. The Ila- ture cf theIe tables will be beA uzaderRood by confultirlg the two pltlns of thelm tovvards tile right hand ill tab. XVIII. n whereof one lepreIellts the two grooves Etted ir the alternate xeceptloll

tf



MeaJremenf nf a Bvfe on Heun[low-Heath. 409 of the horizontal clarnp, according to the iide on whlch tIle rod lies that is to 1zW moved on into coitlcidetxce; alld ttle other {h-ews it adtually ill its placen xvith the cllmp itWelf derac3jed -ia clevation alo-lag;-Iide of it. Thus fit^om the plan- it nzay be perceived, that the -iRrR, oradjuRed rodg lies tosvarcls ttwe ISarv vller efide of the tal)leS and is there fecured by the vertica3. clamp. The Wecotld¢, or tnoveable rodv iies on the hither- iRdes and therefore the horizontal clamp is placed in tile farthelx groove where it is firmly pinched byxthe nut -urldel neathw The rod has lJecIl bLought to coiIlcidellce ly wo^kiI3g with vlae tsvo

milled-headed Screws agaillR the oppofite fides of the crofs iRot This apparatusX although perfed:ly good ill theQvv was fbund to be much too confined in its taature to atlfwer well in prac tices requiring the Ratlds to be placed s^7ith a degree of prec fion7 which could not be eScEted ill tlle field without great lvEs of time; and this was the real cauSe, $ will be fieetl 11ereafter that the meafurenaent by coincidellces with the dea1 rods was given up, and that by contaAs adl1ered to.

Towards the left-hand of tab. SVII1[. tlle plan of Otle of the fquare tables is reprEellted with the ends of the fec;olod and

. y

thixd rods upon 1t ill cotlta2. Irl this operatioll it svill te perceiveds tllat ot-lly olue crofs-fioot of ea£h rod could n4otv reR

011 and be clamped to the Ralld9 tIle tab}es leaving teen ioad vertently cut too fzzall to adtnit of botEw; and although this has-the appearatlce of npWrfeAion yet lwo incoilveniezcy

AttYelO %7aS 60tlnd t0 refult frorn it in pra&XceX experiece havitlg nzesvn tI-lat tlle clalnpiwg czf either etld fufEced to keep the rod fteady. AloIlgfide of the table9 vlle vertical claxnD, being that noxv folely xnade uSe of3, xs llliextrife repltSetlted ia

a

clevatloxl.

't<Ot}



S0 Major Gereral Ros Jccoxt: o tEe On thet face or- exterior fide of each leg- of 5 all the £}mdif

flxed as well as moveableS a plate of brafs is irewed near the bortorn with two holes il:l each, over a groove purpofely maie ill the wood underneathJ By mearls of thefe plate-sy paralklopid leaderl ssrelgh-ts about fourteen! pou.nds each,. havi-ng.,brafsfpin$

wtth lleads filited to ellter tlle holes, and fill dowFrl itl the grooves, illtO a llarrow-pointed part o-f them9 are readi3y fipped otw or ofF each leg. Thus every Iland, exclufi-ve of its own weight which is about thi*r-ty-one poulads, being-loaded s^7ith forty-two pou3lds; of }ead, is therel)y relldered per:iEl;ly fim and Ileady.

A nutnber of wed>$efs were alfo p:repared, arud; aiwvs ready t6 I)e placed under the legs; btr meallSs< of*wshlch, and a-Ipirit level laid on the table7 its platle is broiight toR the^ properS

.

pOiltIOn. . NotwithRalld;illg all thefe- precaution$, it havlng; teEeA-- bund9.

in the meafuretnent with the deal tods that time-was loR in levelling the Ratlds particularly in fituatioris wOre the furEace happened to be more than uiallyc uneven, or where it was of a looWe or fputlgy nature, thereire Mrd SMEATON adviSecl (and no man's advice isf more defervXlg otf attentiot), that deal platfortns,- Ilatldirag o< pickers driven into the gror}nd,< and properly levelled, Ihould be uIEd- to receive the- legs of the Itands. Accordingly, for the operatioil with thae glaSs rods (table XIX.) twellty fuch triangular platfUrms- made of inch dealS whofe fides were each three feer two ilches in letlgth:> and void in the rnidclleS were provided,0as alSoalluVml3erof beech-picketsX about an itlch and a half fquare a<d-of dS ferent lengths, from fevelu to twelve or fourteen illches. Tlxree: of theSe picketsX ffiort or lcalag as the fituation required, beitlg kltiverl itlto the groulldX t11 tEse}r lleads (by the carpeIlterss

X level)



MeaJXrgncen tf 4 BaJa ot HounffiwEIteath 4vg r

level}0were brght to the proper heightS the platform svas-: Iaid upon them ;; a;nd on that the Rarld itilf being placed, itv. pofitiolt was ultLmatelyt nrred:t;ed by the birit level- laid oaA thee toXr of tlle tabE. Each of: it beech picken had a holed boredf through its topj f* to xCtive a piece of Itrong tel1t° Ewe- bygwhichs and the llelp of one of the ca-mp rrlallets the pickets w-ere eafly pulled up a-gaillX wheIll the platE-orrn was t le removed: to. a new f<mation.

Banirng SeleApe oand F&.ods.. Tab $:VIIt. . . .

,

In order to trace- the llne of zoo yards or 60Q feet t}Arough5 the airS from oIle fixed Rand to the other, it was ufualX in t1a: firll place, to-Rrerch a cord ex-tremely tight aIo-tlg t}ae ground,? and to divide t11e Epace into rod leng-ths l)y ftnall wooden pitlSQ placed clofe by the cord, which retnailled thewX and accorditlgly marled very nearlyX the points over which the cen-ters of t11e slltermecliate Rallds were to come. A pieceof woo-dg about- foulteen itlches inA lengthX andS one and a half itl brieadth> paillted white, witEl a narrosv black litle along-t-he tniddle o-f vX leiIag prepared f8r the purpoS, was laid on the furface of - the fa-rther Rarld. T-he lolling teleScope; fourteen itaches long atlds one and a- half-}nc diameter9 with a ftnall tnaglwifying power and moveable o-lDje&-glarsS fo as to ISt it br very Ihort^- IiRances, was then laid on tI1e ftrfice o:E the neareR-ftandt which IJy mezarls of svedges placedt under the legaX had-that- fide t-onvard the fulother lland fo elev$ted or depreflEed as ton brix3g the crofi wires to coi31cide sv;th the black litle otl thew paited board, Twelltywfour boning tods- had been originally- provided X X but: it larely Ilappened, that naore than elght. or tetl

,



4Eo lWjor-General Roo 's Scvo>Zzz of tie of rlaat llumlzer ve-e uiSed iil anyeone ItatIolz. TIley are of- clean dWal upwards of five feet.in letlgthS oile itlch -uarey a11(1 poitwred with plate iron at the bottemo fo as- to be. cafily fixed illto Elle greritld. Eacll rod carriespa creSssvaneX i1x or fevets illGheS iIl leragthX atld three-quarters of an inch in bteadth Frilis croEsvaneX beillgtmoved:.upwards;or downwardsalong the rodX till its u?per furface coillcided -vvith the croIs wires of the teleScope and black lirle on thespainted board its<under fur

S ice then matked the height to which the furEace - of the ffiand was to be brought at that particular place. rIn this manner a certaito tlutuberrof p<3jLnts ;1nEthe¢litzepaIElrlg;through the air firom olle fixed Italad to the other, being accurately-obtained,, it was very eafyX atfiall th:e irltermediate places, Xby tthe appli- CAtiOll of the eye alone Jto the furface:eE iany o1}e Rand or rod, . t britlg the furfices- of the other-ttRands near it into the fame platse.

.

Cup and fripod fior prrtzirg tthe poxnt upQn the ground, wherc

the meaJigrement SWdS ^dJ¢anZinued nighl, and reJraxmed aest

r fSt 7rStng Tab. L;V][II .

It las been already mentionedS atld in giving the account 45 the rougI- meafllremerlt with the cllainS there xvill be far ther>^ occ-adlone t-o; retnarkX that tlle bate was divided into hypo-- thentScs of zoobyarcls or 6OQ feet eacll, helXe Square pickets

werb driven ila:to-the groutldS and regularly ntlmbered, fo as to be eaI1ly referred tcs on ally occafion Ill the meafureme-nt- witll the rods it was cuRomary to finiIh the day's wo$1; at or near;otle of thefe Rations Wherl the rods of tsve-taty feet Were ufed, the termillation of;a rod was?rofAcourSe, always

- - foutldl



Meararence of a Bayre on T4outlnowWHeatIl. 4I3

fiu-d to l)e within ;a; few illches of tlle picket correfponding with the hypotherluSes as detertnined by the chain. 13llt svith the rods of twetlty feet three inctwes the daySs wo1-k wJuS alZ ways tsldexlt with Ca ftaAional rodg by fufipetlding a plumme-t frornsfome conveniellt p;rt of the Rem, marked foro the purZ pofe3; and s which: cotl Sequetltly -became the 0 poli-nt of --cornmence lncll.t wext morillng.

- e

T>1as brafs cups tnade uSe of ion- theSe; occafionsg is of the figure of a1s inverted truncated cone whofeimean diarneter is four inches, and its depth about five, with a very fmall itlcli- nation in the fdes. It was placed in a hole dug fbr it in tlle earthS immediately tInder tl;ze point of fufpenfiorl of the plum mer,- ferving otlly to hoId the water in which it vibratedO

The nature of the tripod will be beIt collceived from the . .platl- and elevatiorl of it ill etal:). XVIII. 1t coniiiRs of two

ftrotlg pieces of be¢C}l wood7 mortoifed into each other, fO as to leSeml)le a half c10fs, or the letter T ilavertedS having three firotlg iroll prongs, abotlvt twelve itaches in- length; which pafs tlurough the ends of the woodS atad are faRened to it by fquare nuts at top 0t1 the filrEace of the tripod lies a firnilar half crofs of mahogatlyS movealzlet l)y lmeans of grooves itl the d reEtio2l of the longeR fide) at-Xel fixable ly its proper fcrewsg >Xvlletl brought to the dellred pO5ltiOn. This mahogany halS crofs carries on its furEace a brafs rulerX noveabletwt right-aagle$ to the forrner direAion9 fixalule alfo l;)y azeans of its ow< fcresvsX and - o11 whoSe etld is cut a verv ¢fine itltelfedtio< Thus anv day's operatiotl havitlg been fillithed tle tloipod ^rss placed near the cup5 with it 1-ogeR fide parallel to the lil3e of

meafurelnetltS and its p-otlgs driveIl illtO the grou;d, fo as to

Ibe rexldtred perfeEt.ly itXnovealJle withoEvlt great violencei trhe plumxnet bcilag thell futpeded by a file gilt wire, at aay 3<;rt



g.1+ May'or--Gexeral ltoo iMcroanf ;f -{be ofthe fiem of the deal rods ihdiSerentlyS but always at the fixed *

or hindermoI} elid of the glafi rods the brafis ruler was advanced fo ruear as almoft to toich -the wire atldrthere tnade iR. - Tht$ being done the mahogany halScroIi was laLily mo0red bacl- -Xvards or forwards, irl tlle diredciotz of tshe line of meSurements until the interfe{R-iong as feeti by a perfon-lying -down vil-tlie agrolllld br the purpoiS accurately coitlcided with the gilt wires whereitwaslikewife faRened:by!its properirews. A ten-t was !<then pit£hed very near the; apparaus, ir the -foldiers who furnilhed the -£entixlel fbr it:s fecurity, till ftheemeafurement was refumed ; and particularly ito gua-rd lt wfrom ; beirlg diAlu^- b,y catIt duritl,vg-the n1,h:t.

-mtfdsfiar¢>2z4tingt gn a peVrffnen ^man7hers -the estre7nvEies f- {he Ba@ Tal. XXVIH

13ebre anj7 awurate >meafi1rePmett could ultmateIy be made <3f the baCe by m-eans of -rodsS irl order thM we-ght with certainI:y xfer>-to -the Kfame poi-nt? oI1 aNy occafion that mi@t arife of cc>rreEl;ion or -repetltiotl of the Wotk9 t -had all along beetl fbre-feet> that it worlld be abSolutely tweceIL -to 11nk deep antovthe grod woodetl -pipes7 I,or fuch like thin-gs at the es- Wtremities of tlre bafeS which could ne be remove(ls or evea diRurbedq, -by idle -er ignorant peopleX without very col-Xfiderable lalDouf, ;:lWr. MYtsz? F.R.S. was accordingly requeIled to

N That this might be co-tvendy done, a moveab1e and was placed, under the glali rod> about four fect frlom the fixed crsd} and its ta-1?le.eIevated till, by

;;oearing againA ttle lowel pairt eof the caSe} it rCceiVed itS w.ight. TH1S permitted . .

=e .Ra}d under the fixed end to be lowered and zmoved; to ma-lie toom br the . .

;.wparat-t-RsO

order



MeaJtlremgn! of a BJaJ on TWounnout=HeathO 4EN erder ts;vo fucil pipes to be provided, about lix feet itl lelugth -cach, atld olle foot itl diameterX svith a bore of four inches it

.

bthe uppermoR etl-d, for the depth-of twoX4fitetn atld crofs-arms ear the losvernloft end, itl >the- Rile of Sthe Cornmow warpitlg

PORS. -AS aIL imPrOVemeI1 On tI1iSridCa NIr. MENE very judicivuRy propofed that, <-infiead- of -the crofs-arrlls, the lo^rer ends -off the pipes {hould pufs through- the nave -of a11 eld coach-wheel, atld then be fecured 'oy a bolxt ullderneath Thes alteration was approved of;- and the *maclaitlesX vtht-ls esecuteda werefent foon after by water to HamLptone

trIle plall alld Ied:iot- of olle of theSe wheets, with <the di{lued flde dowllwards, are reprefetlted towards: the left-hZaM in tab. XVIII. -Nvlle-re it will be lperseived, that by rlaearas o£ four kllee-pipces, rnade of crooked ealf > the pipe is firmly- toltedx to the xvheel9 arld thereby kept at right.-angles to ts qlane. The top- of the pipe is atrO fecured exteriorly l)y an. iroll hoopv atld las a caR°trotl5-l30x dlival into it *N0Thofe inIler

diameteL is fotlr itlchesX atltSweritlg to that of the l)ore. Four oak piles for each wSweel were prei3ared to be drivetl ;tltosthe lbortoms of the pits dug for their reception, which vere fix feet it1 cliarreter and the farne in depth. The foil near HarnE3t0n Poor-houfe being cf a loofe fat-l-dy tlat;ure, t-llere the pilsslwez-e eafily driven llltv the l)ottom, -utltil theit tops wel e oll the fanac oleve3. Tlle flat Sof ti-le fellies of the svheel beitlg then laid on the-piles, the earth was-fillWd itl at-ld wd1 rammed around the pipes qui te -up ̂ to ti1e lfutKface, with utilich --its mt3uth xs wenO But the fOil At KiL1g'S Arbour, beitag a hardboutld gravel) tlle -p1les could not be driven illtO the bottom of thatqpit; where ioreX --tlle flat of tlle urheel refl:s there onsthe grarel OI]yQ - T'lle brafs c-upf formerly -defcribedS wtas frorn the fiX^RnF tended to be LDlaced in the pipes, fo-r wlllch purpofe it -has tsro

ZIOLT IJXXVO <-I i l lids-



Atyor-Geseral Row-§s Account of the 6

lidss one a femi-cilXcTe,-uibh t-le cenFral point marked -bar a- Xiile cut on its dancet-erX l)rougElt illtO the diredioll of the bafe; svith wlllch liIle the gilt wireX fufpendedl at the extremity of the fil^R 3rod, was lzade to coincide orl the comtnencetnetlt of the meafurementX TIle other lid has a very imall hole made in slts cel-lter7 through uhlch theplumtmet wire is to paSs, wllen ftlfpetlded from the cetlter af the inRrutnent, heteafter to be made *.Se of for the detertrlinatiolu of the atlgles at the bafe, or irl any other flatioll whate er, where it nzay be neceSary to

-bring it tery accurately uoster a Oillt ON the irface of tha -grouIld ullderlleatho

Rough tnev/oarewenZ af the :I3af with the Chattns a8d deZer>in tion of the relatifve hezghZs of the Stations by tnei¢?Z-s of th feleScopic Spirit L6eseI. Tab XVI. alld XVII

Having in the preceding defcrwtton of the various lnIErus melltsS orlgitlally provie3ed for the lneafuremelat o>f the bafej fully explatned their cotlfiruAionsy uSes, arld modes of appls cation; and havlng thereby anticipatedX in a great degreeS

what muI} othervife have beerl faid to lmalie thetn ullderdood ;11 any account, bletaded FTith that of the executiotl ;F zlittIc more- llow relnaills to be givell than the jourtlal of our pro ceeditlgs from day to day, alld the ultimat@ tefx}lt of the operation.

After a 57ery t-tedious delay, Mr. RAMSDEN havn-g at Ia produced his hutldred-feet chaitln with the portable tranfit in{irutq merlt; alld havillg lent us atl escellent telefcopic fpirit level, for determitling the relative heights; two IeScions of the bafe 6tiIl$ likewife clcared by the foldiers alld fo progrtIss made in

S ; the



Mefaree/ of a BaJ e on Efounnow HeatiqO 4-X

the third7 we wfound ourfelves, on tlle x 6th of JuneS in readi neSs to begitl the rough meafuremerwt.

Lieut. CoIorsel CAL DERWQOD of 11;s ]ajelly7s HorfS GuardsX F.R.S. had, from the leginnings been fo good as to promife his alElRance ill the operation. Lieut.-Colonel PRIN GLE too, of the Corps of Engilleers obligitlgly lzecatne a

rolunteer on the OGCAf10n; aS did alfo Mr. LLOYD-S F.R>.S a few days a-fterwards a while En{igll REYNOLDS OF the 34th regitnetlt7 who had for fome time paR been etnployed in furS xreying the environs of the Heath, conttlllle(l-that srork sv-ith lSuch rpare hatlds as could be afforded hitn i -ir that purpofe; and 1: is to the plan (tab. XVI) done by that officer, th:at- it willP

. . . .

be lzeceISary t-o refer in any thing regarding locality in what Ilas hitherto been faidS a$ we11 as irl the fubSequerlt relatiotl.

The lower elld of the baSe had for fome titne paR been- dii: Xtitlguifhed by a St. Georgess flag fixed to th& top of - a fir f-par thirty-fives fect in heig,ht; and olle of the figtwal bell-tents Itill rexnained at the Ilation near tlle I*umlner-houfe. A rope of zoo yards beillg made vely iR lJy a Rrong iron picket driven xl1tO the groulld at tlle bottom of the flag-Raff; the other end; ssas carried on along the bafe, and placed at the lsottoln of;-a campZcolourX in a litle with -the lJell-telwt. The rope lciXg woulld arouIld a fErong irotl reel prepared fior the purpoSe, svas thereby firetched extremely tightg a perSotl o£caEloalally XliftiLlg it:

up ln tlle middleX or at other pla-cesX alld letting it drop again b

as to brng the whole into the rarne Ilraight line Five perSons wele lueceISary for tlle proper managenelllt of the chasIl; two-

at each end for its adjuRment therefl and oile tosvardJ the mid clleX to lay it cIoSe to the 1°Lue7 or to bear it up ln ally particuz lar place where the circum{tances of the g-rollLid relldered £;1C11 p^ecautions efefu14 The zero or reat elld of the chaia

I i i 2 bvi<;



4rI &t Maj5r+6eNf1edl OX9S Xc*{ONDt g t#- . ' 7 e

ibeing ITrained back Ic) as to coirxcide svith the ?oint cuf comX

mellceme3lt; a Reel arrot was placed asSered as poW;ble itl tE}e fenli-circular cavity of tile brafs handle at the other end. lnho chainL beig thetrdrawn onX5till thc cavity ill the rearthandleM corlld be apvpliedito the firI} areow, a fecond was then placedoin tleat of the Xnt hatwdle and rO OII until fixEcham lengths were thu$ meafured oS, t wh-ich t¢rminating the firI} hypothenuSe, a beech picket9 fornething more thall an itlch fquare arld about fx;ven in length, with N° I. CUt uponbit, > was drivell intp the grovund till its tlead . svas-s nearls level: ssrith the furface It > is. however) to 1)e rezmarkcd, that the fixthuarrow of each llypo-- thexluSe. was coni:}alltly. 1-efit ill thehground till the firR of tllep Xcceeding on¢ Btas placedat to avoid tile error that.woul-d have stherwtifeatifeniitlapplyingth rcar:*etld of tllechaila toothe picket ilficad of the a-rr3-wru

11>11 this marllaer<we "W¢-oceede.d on thee 6thoff June, t]4..in5

the fpace of a1?Ot1t three hotlrs and a half, cornpleted the firk meafusrement1 of th fouth eaR fedson of< thetbafe, comprehetld- ing theXithLrteexl hypotherlufqs bctwectl thB flagS tiaff and ilatior sagarHanwoorth /S^umrner-fiQuSeX the diRance beiIlg y8 chains or 7800 feet, making afoa yardi > iand the mAeall tcmperature of tlae air beillg 63°4 - t

On the; fublequentRday t}lissfeAio.Xr was re-m,eafured xvlth equal cane} wheEl ethc total extellt fc11 ffiort of the thirteenth picketo}lyfiveitlches AsndAhere it is to>>beolzfet;vedX thata ¢onfiderableipart af tllis AdtSerence prcbably arofofrotn the £ltretchitlg of the. chain-acrofs WDlrey sitis7erS at- the farne -time that the irtregularitics of the groutld ale greater in tlwis than. s11 either of thx othqr ts^;o. fedioily. The ln>call heat of this hywas 65°o

T;he



remen of a BaMe on FJounfJowH:eaths 48I-k9

DrSe operation with the chain was fiufpended duritzg thea I 8th

a-nd I gthb of June, thoSe days having been employed in fettliIng ¢ertain matters with Mr. }tAMSDEN rel-atxve to the deal rodst as wel] as to gilre titne for - tlie makingt of a hSoIdfafl: for the rear end of tlie chaitl, invelatedi by Lieut. Colonel-PetNGLEe trilis tnzachille, whereof the plan at large is repre-fented by dotted lines at the handle of the shaitaf as it is irl-- Mali by the tWQ elevsltiolas adjo;tlitxg ;-n taS XVIi; -:mizifiRs: 0d a femi-c1rcular iron plate, fiom the bottom of whth prdts tvwo double alld one fitlgle prong. Ill the middle, between: £he two double prongs aifemi-circularK cavity is formed, fitted to receive the lteel arrow :on- otIe fiide, wElile that7 i-lw tht brafs reh ceives it Oll the otherO- In a focket ita the-middle; a firong wooden handles retembling: that of a fpadeS is placed.: Thus the rear handle of the chain being applLied to- the arrow, the ioldfaS embiraces-with its double prongs the- Rraight part of the brafs, atzd in- tliat p-ofition, beilag forced into thegroulld by the aSio} of a man at-the handle, the rear elad of t-he chaill is thereby kept- fo firm as to b;e immoveable by the cfforts of- the two men at the otherbend, in firetchingit- to its-true pofition.s, for the front arrow. < :

On Motlday, the zIR of Xutle, the-operations were ref-utu-eds by meafuring tsvice th the chain (fiorwards atld agaill bacli vards) the thirteen bypothenufies cotnprehended irl the Necond f-eAion of the l)afeX between Hanworth SummerbhouSe arwd the north;*well lzank Of ithe great:!roacl+2;(atl old R:otman way-) 3eadiag frorn Stailles to London. This beitw;g the fmootlaeN ljeiart of the) HeatIz, and the holdfaft being rlow applied, the two meafurements- diflfered otaly one inch arld a half in the diRance of 7soo fect This inItarlce of accuracy is alone fuFs

iG1mt



4:o 7r-iGeneral Rorrs i:vcotln of the ficient to prove the great excellence of the chainS althou$h allothers will;be gierell llereafter Ilill nore furpriftlg.

On the fame day that the fecond feEtioll of the ltafe was meafured, the Ievels of that and the firR were taken. The

.. A . i ' ., , ' e , ' ; ' -_

operation of levelling is CO univerfally knossrn, as to relader ally detail of- it untzeceffary. It will be fufficietlt to lEayv that the Epirit level rnade uSe of on this occafion was a very good otleS

about eighteen inches in letlgths and could at all times be very rveadily atld accurately adjuRed by itlverElorl in its Y's. The tops of the piclQets marking the hypothenufal diIlancess were the poixlts oll which the levelling rods were placed on each fde of the level; whlch leing-itlverted at the lntermediate picket, points equ;*diRantr from the ce-lter of the earth were thereby obtaitled, at the crofs vanes of the levelling rods, and no cor- redion for curvature or refradtioll necelqary. It will lte readily underRood, that the relative heights of the pickets were found by tneaEurila-g their diRances from the centers of the croEs X awes and asis of the + telefcope reppeEtivelr.

The filx firll colutnns towards the left-hand of the firll or geileral table fubjoined to this Paper, Shew difZ tin2Iy every thitag relating to the levels of the whole bjafe? thefe; of the third feEl;ion havIIlg bieen determined on the 2zd of June By examiniIlg the tabl.e ̂t will be feenX that the a{Wat oz1 the fir{E feEtioll ow -I0.555 feet,

an the fecoild ^ M*58o ;atld on the tlaird * <1 2. I 3o

toti s s 3In265 iet7 >-

tween the lowel extrernity tt Hampton Poor-llouSe and the higher tlear Kirig's-ArSour

O

5The



Me"J*uregen of a Bafie on Hounnow-Heatti, 4zz The colnputed numbers itl tlle feventll columtl are the

reduEtions * depelidillg oll the aforefaid tleights, or the dif- ferellces between the l-lypothetlufal- diflances of 600 feet each and the reduced bafe diRallces. Wittl regard to the retnaining coltllnlls of the table, or thofe towards tlle: rig}lt- halld, they will be feverally fpokei] to hereafter, ili taki:X}g illtO COllrlder&-

tioll the expatlfioll of tnetals7 as determined with great accuracy ly the experiments with tlae pyrotnetei.

LIitherto 1z0 ufe had beeIl zlade af the trallfit iaRrumeIlt: . . ? -

for, in order tllat it lmight be apFplicTS to advYalatageX there wa s a necefI ty for layltlg the zwlaeel itltO tlle groulld at the lowebr Send of the bafe7 and fo to modify the St. C;eorge's flag-fl:a-S 'that, being placed ill the p-i:pel it mi-ght be fteadily fupportea by braces sa a true vertical pofition ;; which we Routldn fkom wexperieace9 could lot be eflided 13y ropes onlyO

The wh-eel bei1lg accord;tagly laid ill its place, and the other preca-utions taken fbr fecuring the flag-Raff, whicll was like wiSe paillted white, that it might be more di^IlxnAly f-een from

s The red:uAiow in the feveBth columns I have computetl by the diSerence between the httare of the hypothenuSe9 aEtual-;ly meafiIred^. and tIi-e fquare o£

.s . . .. . . ... .

thcheight found by ttle leYet; and Lleutv CColonel CAL])ERWOO:D has done the fame . . .

thirg by a much fhorter nzetlsod. Ttius, in the annexed figure, CE being the hypotbeauX of 60c fect, DE the / > serpendicular heiSght obtained lDy levelling, DS the re- l z 0 duEtion required, o-r the diSelence betureen the hypotheZl< / \+ nuie and true lbafe, then, fubfiituting the chord BE in-A C: DB

.

fcead of DE) the fol}owing analogy is obtasued; AB: BE :

BE; iDB; confequelltly, AB-DB: that is, the fquarc of the perpenclicular

height being divided by double the alfiance9 or I 200 feet, the quotie}t is equal to DB the reduEtiony without fenfible error For if DE were four fieet, the greatelt perpendiculal height ili the bafeJ BE the chord would only exceed it -;R5R5 ,,i5B, nThich wouid not be more than wrsw part of an iri.ch. The difference between thc refults9 by the two modes of computationa is fo ttifiing as not to dtierve notice

the



Mqj'or-Cereral RoY''s Hccount oJr De

tlle fartlaer extremity ; on the 2zd of Jutle, the tranfit illRm - tnentSwas aXuRed over th:e thiirteenth picket at Hanwortlt Sumner--houIe? wilile direEted upon the^.flag-aff. I3ut it lzeiilg now foulld, that the vertical plane paIElng tllrough tEle flag-ftaS fe11 to the eaRward of the cetiter of BanRed bpire, therefore the tranfit svas gradually moved to the eaRwardg untildby - repeated trials the three pOilltS were perceived to be in the fame vertical planeX whetl the picket was moved, atldW r-e-placed exadly utlder tIze axis of tlle teleScopen a few illches from its firR pofition. tRhe fame operation was repeated at the twenty- flxth Ratlot-lX oll tlle farfher batlk of the Staines Road; andR laillyS at the forty-fiXth, formitag the tlorthweR extremity of the bafe; where a pit was immediately dug for the wheel, which-was placedithereinS without however filling-irl the earth for tTe preSetaStn rllat beitlg deferred till llear tlle cornpletiort of the meafurealetzt svith the deal rods. Thus the -tsvo extre rllities, atld two itltermeliate poillts of tlle lDafe, beirlg accuZ rately placed, by the help af tlae trarlfit infltrutnellt, in the lEame vertical plat*e with Banlnced SpireX it was eaElly feen, that Nby arratlglt-ag ca-mp colours itl the ill'tervals at axly tirlle, all the other pOilltS tnigElt be brought fo lleariy to coincide with theSe firR, as tlOt to occafionv by devintionX atly {enfible error -in the meafuremelat afierwards to be made. TIlis apspltcation of the tranfit Rveved ..tls) hesvever that fome labour tlad..beell.loR lJy

slot ufitag it Coorierro tfor at the Staitles Road the tr-d cleared vby tize foldiers develateil about two fee-t at:ld a 11alf too much to

the weAward fol t:he tr-ue lirle<> atld at Witlgss Arbour it was . . .

--tsvice as muchX Go tllat we wtere nosv obliged to -widveru the icleareditradc, by adding tovthePeaftern fide of it.

OZ1 the fame day that the chief points st1 the bafe sve-re Exed tDy lB¢allS of lthe tranfit atld the levels of rthe thild fedion

Wtake;



lWq:farr,ffntaZ f a BaJe on lEXolln{lowtieath 4z3 taken as leforesnaelltionedX tl<e rough mearuremetlt o-f t-hat fiC2iOIl with the chail-l was conaplete-dg aLld found Eto conftaia

nillOtetn- llypOtheUrAl- dl)ancts 05 603 f-eet eaclzS alld ot1 o-f 4O4.55 making in tlle -whole II804n$5 ifeet, letsreell the twenty-f1xth Ration at the Staitles Road atld-tlle center of the pipe ear Killg'$ Arbour, -the mean temperatulJe beiag 6X°X Here it is to lDe obServed, that this laft feEtion lras oLw1-yg meat

;(ured once with the chain, the tra2-not be;itl-g yet filfficientljr cleared to adn;t of its beillg dorle: to the beI} advantage; and,; whetl completed, it was judge(l to be l)etter to proceed d-ireAly sn the operation with the rods} vthall pto lofe time--in tfhe ufual- repetition, f<nce the merits of the cha-ln, in this way of apw plyiIag tt, were already fuiciently svell ell:abliJhed; aIld atly future teIts to which it was to bne put were propofed to be o£

* * 1

a-more rlglu natu-ree When the lerlgtll d;the chain, i-n lts original fiate, was

aCcertairled by -the dots on the braSs pitls o1z the New-EIlgIand -plalll it was foutld, ill the then temperat-ure of 74° to ex ceed the IOO feet by near olle quar:ter of an ;nch7 or o.x4s -illch. TIlerefore, in the vtenzperature of 63° being tllat in whSich the Iengths of the deal rods were la;-d oR, and diSering rery little from what svas likew-ii;the tnean heat -of the air, when -applied upon the Heath, the -chalab according to -the experi- ;ments on the expalafion of the ve:ry fame Reel, would ex£eed ;the IOO feet by O.I61 nch, or O.OI34 -foot. 0Hetlce the fum of the thLee feAiolls of the bafe, z7+ cllaitls,> being mVul- tiplied by O.OI 34 foor, we a11 have 3.67 fe-et fo-r the equ-ation of tlac chairl ++ ss feer, to l)e added toits lellgthX svlaicll svill then become z7408.zz fe-et from the ceilter of one pipe -to the fceIIter of the other: and this srould haxre lJeerl tihe true -leIlgtll -of the bafe, as given t;r tlle rough meafuremerlt with the

YOL. LXXVW K k k GhainX



4m4 lMI#or-General ttYi Accognt of i thet chain, if the fusrface had beetl one uniform incllned phne-- th*ouighout its whole extellt ButS although the aScent of Hounllow-Heath is -fe fmall,: and b gradual, as to eccafior<;:

. .

little more than half aXtl it1-ch of redud-ion, Som the 46 hypo; thenufal to;theW 416 baSe diflarces, into which it-is divided7 as

mayLlJe feen by refirritlg to the table; yet each of thefe hy pothenufes colataining nagain maliy ot->her fmall irregularities, all af whi-ch affeEt tEdle meaftlretnent by the chfain, iIze proportion to ttheir trumber and height, n<; every f-ace of 6to feetX their- urxitdA effit?Es, itucluding the laterat deviatitls from the t-rueA lllle itl meafi!urings do fomewhat more thatl con3twnfate for thes extra-lerlgth of the -thainS asswill be Seen hereafter in com paring the legth d t-hep baIb 3ou^ now obta-Xd. with thatt given by the rods.

The weathers which duritlg ie greater part of June ha& lbeerl wet, became {liSll lror>i towards the endt of thesmallth and frIt wseek of 3u1y; rO much fos tI}at tven if the deal rodst had been->ready they &ouldnot hAave been Ged with advantage. The folXdiersj neverthelei; were not idle> being, whets the; weather mtot+zlde permitX partlytemploye<3 i in cleariE tlae EI:eathf and pvtly in aIdiRiag :A@Ir. RE-YANOL:D5 itlk the furvey towurd$i the perEdtit?g af nrIhich matly chief points we>re fixed bya means of myt-altrotlornical quadrant5 phlced fcr iat purpofe atW

ilieveral di:ffelent :Pcatiotls of the baIb At this titne too (July< Sth) -Io levelled from the lower elld of the bafe to the furface of the Thames at iIampton, atld; foulld theb deI;zeal; tosbe 3.&<X>P t¢t0,

M- 0aregeat



AIeay4aramenz af a Bfe on hulinowflatht ,

p

dF,; s

MeaJ"rement of the Ba/e -with the DeaS 7?odso Tab. XVI. anci XVII]Ee

Such estraordinary eare and pains had been beRowed 1ll the

cvnRruStion of the deal rodst in order to render them the leIt which had ever been made, that9 although l)egun earlyill June, they were tlot complerely filithed before the Isth of July. They were brought that afternoon by Mr. RAMSDEN,,5 together wi-th the various pares of the apparatus neceIfary for their applicatioll ilu rthe field, to Kthe camp now moved frotny Hanworth Summer-houSe to the interieEtion of the bafe with Wolfey River; whence they were tranfported, early next morllirlg? to the pipe rlear Hamptoll Poor-houSe, dere we were met by Sir JOSEPH BANKS, accompanied by MeS. BLAG_ DEN, CAVENDISH, LLOYD, an-d SMEAroN, a11 ready to letld their a{ElRailce in the fuSequent mer@furation.

BeCore I proceed farther, I think it here <fincumbenit upon me very glSatefully to remarkX that the refpeAable atld very wo<hy Pre{;dent of:the:Royal Socletys eve-r ze-alous in the cavi-Se of fciellUe, aIlz1 who llad repeatedly vifited the heath5 >to

oWer aid7 if fuch had been neceXary, wSte.the firI} and rouglaer part- of the operattolls were going on; norv that othe-rs of a more delicate nature ssere to commence, at1d where it s of lmportatltes that thofe eri-tl uRed- svith tlle execution liouid meet svith as fewS and a-s¢flzort, interruptloIls as poIMibleS -n olily gave liis attetldlance from-lnartwitlg to nigllt in the fieild, durig tlle whole progreSs of Nthe srork-; but alio, witih tilat llE)erality o-f mind ̂hich di{tinguiIlles all his aSiorls ordereci his Ztents to 13e colltinually pitched tlear at haIld, wlaere l-l>s iin:tnediate

K k k Z : guefEsa



*42;d ltUor-Sntal'.RoY'M Actant; f-t

'Uefi59 and the nulmerous viStors XtholYl curiofity drew to tIw

fpotg met witrhs th-e -rtwell hofpt2table fupply of every neceWary and evetl eleganit rc-freth-meilteS It wlll eafilf be imagirled, how great1y tzlais^-tended t) expedlte the work at<-d how tn-uch more ¢omirtable and pleafa-llt; it ren;dered the l:>al)our to all wvho;^ obligillgU>y took p-alt Lllv it ;. but mote efpecia-lly- to himu whes beirlg a volulltee-r ul it at fir> cotaflerede himl:elf as boulad tcs-+ perreVere 11] -i& beR endeaslears to brzlg it to - a fuccefsfu1 con cltlfion.

From;ttie defcriptiotl thate has beell; given of o t-he deal rods, it will bW rememlDeredX that qtIley are fitted to be apjplied itl ludeaZ iringX either by tShe coilcidell-ces cf lines in:laid one inch and a half from each extremi-£yg or-by the COullt25 of de fpilericaVl lips of the bell-lnetaI;svith which they are tippeds Thx firI}g feemizg to be-the rnoA accurate, Salethough the moR^tedious method, was that btr which sve pro-poSed to fet-outOv

lthe flag-Itaff having beell previou-i[ly retntve(l fiom- the pipe, alld the braSs cup Slled with m;tater put in its Read, allL the neceSary precautions being likesvife talierl: for preServillg the litle of diredion horizotal-lyg Sby the rope firetched along; the firk liypothenufeF and rerticaLly, lDy mealls o£ the boninb rods s the SvI} tvory line Olwl the fir{t rod w^7as brought- by the lplumtnet to cei-llcide with the center of the c.up, in which pofitiotlg being clamped, it acctlvately marked-: the comtnencev mellt of the lDafe. Tlle fecond rod beillg now applied to tile firfE, atld moved up by; the app-aratus fortnerly defcribed (tab; XVIt:I.) till its lille coinclded wit-h th-at ollF the fir-It; and, ill like matlners the third rod being applieci o11 the alternate fide of the fecol1d, rnos7ed u}? and clarnpedsas the refil; thus the cxaA diRatlce of fisty feet; was aCcereained, care l)eing always taken>: that the ErIt adju:Liments w:ere not diRurbed; while the

fulfeqvle.-rst



MPfwfire nf a Bve ¢r HoUnow-HeathO 427- iSSquellt ones- wer-e fbrtnLtzg The clamps- fafl:etling the fi rk md to itSt Ratlds leing tilletl detachedS it was carried by twoX rne1l and laid o11 the alternate fide cif the tAhird; atld d OL1 itl-

£t3cceid;0tls until ISfteen re3d letlgths svert tneaEured o3E beilg the llalf of the firR-- hypothenuEe.

The time confu1n-ed in meaEuring this thort-^di-hnce of 3oo iet was llOt leIs than fiV>e hours; owirlg as- has been brmerly metltio<ed to the confitled+nature of Kle apparatus for movilS the rocls oll iiwrocoincidenceXwhictl reqtlired7fuch laicety ila placing. fhe Rands> as could- not le effeAed untiI afEer feveraI repeated! utlfuccefsful trials All the-esecutive- people w-ere t-herefore ofN opinioll, that it would be proper tQ dikontitlue> this lnede Qf

nlearurelnellt, at leaR utltil a tnole co1lvellient appaPatus CoUlult

be thought of for the purpoSe ;^ ;and that, in tlle meall ttine. we ffioultl proceed by the naethod of coiltad-Svi as the ouly ill^+ teraative we couidRf8r the preferat adopt$.

The rods being accordingly placed- itl con-taA with eachs tther, we fooll nade -greatr progrefs- fitliiBing the operations - of the d-ay at the rnicld-le of the fourth hypothetluSe whered Kle tripod, svit}w its guard, was placed7 to preServe thepoint of connencementt for the ellfuing morlaitzgo

* Althou-gh;T acquieRed in tSe chanffl thus hbconte -neceffiary yet lt was WitELo

much reluEtance} becaufe it 1eA ulldecidech the conttfied pointiwith regard tos coincidences and-contaAs If ure cotllul hav-e proceeded uRith the coincidexlt rods t;11 eighty.one+Iengths-vltere meaired of and then mea-fure-d bac.k th-e;5me fpace- lby placinSg e1ghty rods irl conta&} theB point wotz:ld have b;eerz cleal ly ittled. For if the termirlatlon vE the eightieth roeI agreed esaEtty with the.point )f departureg ceElta2s being the meR expeditlous would have been jud$ved the beR method. Vn the contrary, . if the eiglitieth rod feIl Rlort - of aeaching r be pt)lt] t of deprtureX t there could have- been no doubts that the dixSerence muR havc 3rlieErolaX liuttirlg olle lod-againA the other whereby a <^ertairl finall pa^oportxon of each rod; came tq be lofi iD.te..aCCOllIltx by beiag meafured twsce¢over f

Thi..s



+aS Major*General R6Y9S jqcc:oun of tbe TEle meafuring rodsS when put into the che in Londons

had been compared and folllld to agree with the Ilatldard. The compariCon was not repeated oll tile i th ; lout this bei1lg dotle on the xyth, at 7 h. A.M. vlilder tlle oil-clotl] carlopy at the mrlzp, tthey were foulld at a medium to excefid the ftandard by oneJfiftieth of an inchg tlae temperature then beillg 6z°. After the coluparifotl they were carried to the place of the tripoa whetl the operatiotl was refumedlJybritlgillgwith the helpofthe plummet, the fame pOiIlt of the rod with which sve had left of work, to coillcide with the interfedion on the brafA ruler The meaf-urement of this day sras clofed at the etld of the tenth hypo thenuSe, whexl the rods beingcarrifed leack to camp were com pared, atld found accurately to agree with the Randard.

A confiderable 511 in the barometerX between tEle evening of tlle -X7thand the morning of the Igth portetlded raitl A+ie- rerthelefs, all parties r-epaired to tlle place of rendezvous, svllich sras appo;Xted at the lower end of the bafe, itl order to

re-meaI7ulJe the two firR hypothenuSes, by placitlg all the rods ill contaXtS svhich on the I 6th lwad been clone partly orle way and partly the otEler6 The operation beillg according repeated trith g;reat care, thP poitlt of the fistieth rod which forlnerly correfponded to tWhe cellter iof the fecolld picket, was now butld to lJe pullled forward exaAly forty-five inchesS anfweral)le to the4deficierley oll tlae Efteerl coincident tod with which §tle- menfuration u7.as tJegtit6< It nosr bega] to rain therefore the rods were carricd l)ack to camp, atld beitlg Severally compared,, tlley wrere fotl<lci to excecd the flandard each by one-tElirtieth of atl illClls occafiowed by the extraordillary hutnidity of the air. A;lleavy rai-n eIlftled; aIld svll;at made this much more*regre;ted by a11 wasX tlhat ill tlle foretloQn tlleir MaieIties graciouny cont

detcellded to eholaour thc catnp wittl their pre;ixse, -alad cOl- :inued



MevEreanen! oJC a B&e dn HoutXosv*Henth. <9 ntlued there folne titne; but the weatlzer-becoming rather worEe, it.was utterly irnpofEL)le to Ihessr their l\taJeIlies the nature of the operation, by ally prog;refs that could at that time be made ilu the ssork.

ftfter a cotltilluarlce of unfavourable weather br feveral ayS9

theoperatiorlswererefunled atgll. A.NI. ofthe23d whenfthe rods being compaled wevre fbutld Rill to exceed the Randard by o<e-tilirtieth of an itlch, alld the tsmperature ow was 6I°lv

Here it is to be obServed, that inl our progref$ forsvard, an accut rate regiRer had- been all aloIng kept of that point of cach rodr correrpolldiIlg to ttle center of the hypothenufil picketsS 1Zy wotirl; its dillalace from either end, whereby the error of tlae cllaiIl at each Ilationb svas readily diScol7ered, at rlle fame time tljat the vevolutiolls of the three rods fervedl to keep the accountP of the total meafiuremellt. II1 orde3r9 therefore>. that this mo thod might l)e diSlin&{y adhered to, it was judged proper to

puSh oll the rod that lay over the triped at N° IO. exaEtly forty five inches, to make good the deficiency of the firll fiEtee:n coincidetlt rods, arld that the account mig;ht [3e kept;from the. Iower elldu of the baCe in tatire rod5 of 243 and completo revolutions o-f 729 irlcshes each. This belrlgA dene? the reI}> were placed ill tlle orditlary icceflion; and wefintfEed the bu{;nefs of the day at the tigllteenth: Ilatiot]t>-where the rods beingwcompared at 6 h. P.Al. their mean length was foutld to exceed that of the Itandard zJth part of an ir<hj tlhes tetnpera ture then being S4°

On. Saturday the z4th of July the rods were tllree tlmes compared ,; at 7 h. 30f AeM I I h. I S' A.M. a1nd < h . +5t P.M Their rnean excefs above rlle- Ilatadard was fouwd to be o-le-

. ..

thirtieth of ail ;nchs and the meatl gevLwt 64° In the coorfe Qf

t-hc daa the nweaQuremexlt wasDcon.tillued t1o1n the eig;hteenth toI til;



+3OE Mjor-Cestral:''RoY'ss Alzvo8eZ f the t-he twentySevetlth IlatiotaX or fi:rR of the third feAion of the I)aKe where the triped was placed as ut1ulal; aald -there it reo mained ulltouched7 oll account of bad weather till Molld'ay the 2d of Augu.

Cotlfidering how much time alzd lal)our had been beItowed itl ol)taitlitlg what we certaillly had cvery reafotl to conclude were: the beR cIcal rods that ever were rnadeS it was no ILnall difap poitltme-nt llOsv to find, that they were fo liable to lellgthell alld (horterl by the humid atld dry ates of the atrllofiphereS as to leave us tlo hopes of being able, by their meallss to deter- mine tile IeI}gtlS of the baSe to ttlat degree of preciiRow sve had all alotzg aimed at. But fnce more than onehalf of it was already rneafuredX it was judged proper to proceed with them ia their prefellt llate, alld then to has7e them carefully painted-or ararniihedX bSefore they Ihould be farther ufed

The ullfavourabletlefs of tlle feaforl, atld delays irl obtailling t-he inArumetlts had already beell tlle cauSes of; prorrafltirlg t-he Operati3tlS OL1 HOtItlflOW*HCatll greatly beyotld what was at firA expeded; aild tile fhilure of the deal rceds gave ao imme- dlate profpeA of their being fpeedily brought to a c-otlclufionX C3n revolving ill my owll mind the diicretl-talterllatives wte might ultilllately be obligecl to have recourfe te, metal lods olf fome killd or otherg wh.oSe cxpallfian could always be determined by experiLneatt, See-med to promtife a rel-fult that -mrighe! be fafely relied o>o CaI} kirolu was what I had thoughtts of pROpO]tigv ktXlOWItlg frotN an experimen-t svllich I had made myfelEX tthat it expanded lefs .thaal :Reel The curnberfomenefs .of its weight -appeared indeed ol;tieR-iotlable; but that ill-COll

velliell.Ce was either to be IBbmitted -toX or one o:f another kind ;namely, the reduAioLl of the length- which sv.as always, if poffilbleS to be avoided.O

^s



Me+rtmen! of a 134fe on Houn;fow-:Heath. 43 r

At tllis titne lLieut. Colonel CALDER#NVOO-D could NOt CQI1Ve niently leIld tls bis ailftance itl the 15eld; but he viSrlted- us occafionallys, at1d- ot1- om of thefe viElts propofed toAmet that

afs rods lhould be made uSe of inRead of deal; putting ne ilx tnild of another esperiment * that I had madey which Semed to £hew that ft)lid glafi 3rods expallded lefb thall; tubes This pro- pofitiotl the Lisutenant Colotlel:9 befor-e: he came to th-e heatlzS, h;ad made to Mr RAMSDEN2£ who appeared averfe from tnalding the tria1, becauSe of the great length of the ros3s-; atld the brtttletlefs of tliei n:aterial. lE^tevertheIefs it being fulfficielltly Obvious tleat glaSs rods or tubes - of tI}e- i1 - length- or lUme thiallSg ap&proaching tou7ards iXtfl utould be much foQIzer provided. than any lmetal rods whateverv and the favillg of ti4me. beiiag

a PCHnSt*Of COB^fiCqUE1]CCA;KEXieUt. CQ1011e1 CALDERWOO:D vvas ac^¢ cordillgly requeRed*-to tnake the trial at the^gtaSs--houSeX as fooll as poSible after his returtl to town. Next day he fucceeded ina gettitga- fine tulje drasvn eighteen :xCeet longX atld- about ozze ulch- in diameter, alld there imed to be -no 10nSer azr doubt thatYthofe of the proper letlgth mlght be obreLined. 1t nras fouta4d, that folid glaSs rods of fuch extraoldinary dimenSotls eould not be had) it leing irnpoffillzle to talie-at once a fufliclellt

m The experiment liere alluded to was nlade witTi? iN4r. CUTM M IN G9S pyrometC%q

which from its confilhud?£ion did not adnzit of a very F£CrAtt tfitmatiOn of tte

Gieat commvlnicated to the Randari bar7 the rod, atld tulze refpedively. Eltiltl9.z

therefore, the natures of o thte glafs rod-and tube; nlade *lfe o£ at that t3-mCx m\lti.

have been very diXerent, to cauCe the difference of expanfion-; or r-me ju1l Rarlce in the inRrument utlattended.to had occaElotled tIle hllaciotls alzpearance fpritwiLlbe islld, ftoiMt.heexperi}nentsheremfter to begive:nindetall, that-a- lblid glafs pendulum rod expancis fully a-s nlllcti as, n.ay- £1 ttiis partictilar lnRance cien more than-a LUbt; bUt diirent glafs,* hav-itag di¢eretlt fpecific gravltles^ Will no doubt be iSceptible of diXcrent degrees of expanJibitiso

llOL. lLX- L 1 1 qvaxtity



433- Mny'r-yeteral toYS Xcc.DEt.8 @ tbC

qualatity of the XneltecR rnetal on t}R;e irol^lsS -made u-iE of Co-r 41ra^ring them at the gla{s-houQe. - vlnhe week of raixly weatEwer>: vlwich -etwded t1<e month of

July,<cafiorliiag, as has tteen faidX a total fXfpellfotl of the

operatiolas otl the Ileaths vvas employed iti procurit-lg a fuffi-

cieil-t tl-utnber Qf glafs tuSes (otle wliet^eof was tot lCrs ahal: twenty-fx feet long3 alld regulatitlg with Mr.; RAR&DEN every thitlg concertling their-co1lRruAion ilzto meafuring tods. The defcr^lptiotl of thetn we ffiall however defer until the t:ime tf vlzeir application in the field, after havillg finithed the operaZ tion svot}l tllofe of deal.

011 Morlday the 2d of Au;u{^, tIle operatiotls oll the heath -znrexe 1efumed at 8 h. 3o' AM. by coanparing the rods sitll tlle Randard rhich tlacy were fourld to exceed by one-fortieth of all inch, tlle temperature t:lherl beillg 66°. The forward clld of the rod nosso placed over tl1e tripod at N° 27 com-

pletitag the 80c3tll lengtll,- reckoned from the lower elld c3-f the baSe by rods of 343 inches each X artd thefe beirsg equal t0 8IO rods of 240 illCheS-; it WaS judged proper to naark a point ElpOtl the groutld correfpondltzgto this forward elld, that it rnig;ht be referred to in returnitlg back with tlle meaisremellt by tlae glafs rods. Tluis 6vas done by finkitlg two finall pickets liltO the grotltld, about a foot afunder, olle on each fide of the l)aSe, and at right angles to it. A flk thread being then firetclleci over rlle tops of tlle pickets and gently moved 011

tt11! it touched tlle filver wile fufj?et1ded fiom the end of the tod fine notches nvele then made stlith a pen-ktiife irl the tops

cf\the pickers wllereby the threatl could be replaced ill the- nze fltatto1z > svElich being done, the pickets were cosrered over xvitll ealth. In the collrCe of this day nine hypothelluSes were

azeaSureil 9 alle at 7 h. P.!\l. the tripod was placed at thz thirty- flxth



l¢IeaJ2regent- of a BH on-- }4founXow^Reath <3>- i;xthE lXationF The rods7 lJe};ng 1lowt cotnpared, we-re YfottldS to;

agree with the Randiard; and the tempvature was 67°oo 0X1 Tuefwday the y of-AuguIEfi thg to were:cotnpare

at 7 h. A.M. and foulad otlly to exceed-: t;he fl2tldard bv one- fixtieth o-f an iXnch-. Being a+rrwe&0at ti middie of the ioJ?ty

frR hypothetluSe, a point correI}or}ding; to the forvard e:ld-of the I:2IS6- rod was transirrec} to the: ground by the- doub1e pickets alld fi:lk!thrieadg as had; been done at-the twenttr-fieventh Ration The meafuremeIlt was then Xc-onanued to the north- weil extremity of the bafe, wllth was- found in the svheRe t-o contain 1353 completAe 1oig rodiSof 2438 inches each +2I:

mches Where the: trspod;--;wt placed; sn the poim svhich o£ courSe correfpollded -to the I:37oth fiort tod of 24s inches each? equal tos 3nS8ooX inchesy or 2-74oo feer.¢ To wllicIlt difialsce we have- yet to add 4.3.Ii Set, being ie bace inter- cepted betweela the interfedion- on ti tripod and the center o£ the pipe marking the northwe atrem}ty of the l;)afe; whofec total lengthX as givell; by the &a1 rodss witllout regard to es"< pallfiotz, or reduAion - of the hypothenufal litlesR l)ecomest 27404.3I feer. And he-re it is to bel obServed, that t;h:e itaterZ id1011 orl the triped termtnarlng the a74O>o feet only over*Dior the picket a£lofwerillg to th--e 274h- chaill by two itaches alld- mine-telaths*- 13-utv this ntce agreelnent betweetl the refult by- the deal: rods>: and: that-- ittlied by the rough tneafurement witla the chains arifesb from the extraletagth of this laI}, whicS I3 nearly- compenfated- for all the irregularities of the- furfice.

Tlle- meafurement with thev deal tods being fitliIhed, they were compared: at-- 5 h PLN1 atad found to agree with theX htudardX the; tetnperature then being- iAy°a

Expanfioz- P 11>;



.A!.!1;arGene,ral RoY's SccX-t.. ;.f .ttt 2

Bsp48Px of t Dval R§ise

lt Tlas IDso an opiniorlq getlerally enougllX although, as <e ilanre feen erro.zeoufy received that;- very ;Rrai;ht-fibred dea-l svas not at &119 or but littles affeAed-lollgitudinally kY the huZ inidity of the atr That we might 1lot lze led aIlray by ti ull ang to fillacies of this Cort, the Randard rod had beell provided; which being always clofely jffiut up in its cheS, except durig tlae thort lnterim of compariXn could Sel lbut a Mall propor- tiOIl of vlle eSeSs which the meafiuring rods fufferedX thei teitag cotlRantly e-xpofed to tlleXopen air throughout the day, as well as to the moiRure of thet night when lyitlg utlder the o;1-cloth CallOp,5e ttIC fiandard rOd it iS true, col.ld not be accurately compared with the brafs-fcale: fUr altllough :;whe colRrtl&ed9 brafs pins, forty itlches 0 afunderS ̂ had- been- drlverl into its RernX folo the purpofe of fuch cotnpatifonS yet theSe had afterwards lDeelu difiplacedx or aCt leaR the-po-itlts upotl ttlern defaced by the platling over of the upper l furXce lnhis cir- sumRatlceS which was unattended to whetl the operations commetlced is now of 1lo conCequence fi becawSeS from -anf ex-

perirnetlt hereafter to be rnetlti-oned Xth-e lengtlaetliIlg of the Ran- dard tnay s pretty tlearly aSceltained.- But fince there are Ibuze contradidory circulnEcatlces fOOt1 to be mentionedS in the ope ratiotl sxitlUl th-e deal rodsv svhich vi-orlld have made a repetition of it abfolute3y lleceat^y if we had nQt NONV tol)tained tllOfiO of

a diirent killd Io very unexceptiollal;)ie in their nature atld tnode of applicationS asw itl the prei:ellt -cafea to adlnit of no

colupetition between t3at two reXlts) and to render it-improper oI1 our part ever to havc firthers reGourie t:o the f1rft; fo thel-e

can



Hearemenf of -a B on Hounflosv-:L4eath. - 435 cata be littIt doubt, that deal rodsDwill be ulliverfall3r rejeAed lty otIle1* countriesv ill any meafurements tlley may have oc-caGor to make ill futurea

Alsout the Ioth of-JulyX two rods, otle of New-Eagland alld the otller of Riga deal, being meafured by the fixed pOitltS

in tIle great plank in Mr RAMSDEN'S ffiop, and havillg each tvo brafs pilAS drive1l into them at the diRance of tsveIlty feets were laid on the top of tlle houSeX svhere they remained lntil the z6th, the weatherX for the greater part of the timea having been very wet. They were then taken downS and being, by means of the long beam compaliesX compared with the Xmea- fures on thewplank, the New-England Hod was foutld to -have- lengthened o.o3 I il<chX atld thx Riga rod o.ot I illch. By whict experiment the faA Weems to be eIlathlinzedX that Riga red wood, rlotwithIlandillg the quatltity of ttlrpelltine s*hich it contaitls, is more fubceptible: of the efEeEts of tuoiAure tElatt New-Englalld white wood. Mr. R AMSDEN likewife filldss that the great platllt fo often mentiotwed, fuffcr$ in ordinafy fummer weatherX atl alternate expatlf1ola and contlaAionX amounting at a medium to 0.004I of atz illch every da7: tIant

is to fay7 if the diftance between the twenty-fect brafis pOilltS

be snearured firom the fcale, by means of the beam compalles, in the evening, it is foulld to have lengthelled llext morllirxg o.oo4t of an inch, loy tl-we hulmidity of the interve3:witlg 1light. I1< tlle courfe of the following day it contraAs again to its for- ner length arld fo oll. Mr. RAMSDEN Ilas ofte-n obSeloved this alterrlate change irl tlle deal plank; but it svas particularly oll the I 1 ttl aad I zth of AuguIln that ttwe quatltity vras aAuallr lmeaSured. It svill readily be utlderl[iood, tlwat any dizlc8re<ceof ten?eratuloe wIlicll migElt have happened in the btafs fcaleS a^t

* the



436 mior-e.n.eral eYws. itcQ"nt < *>

etlmes of comparifon> wXas always mte£iJ1y takell sDt-o ti acco^tlnt^.

:>wy from this lafi- experiment it§s Sems proMblegr that w-e ffiallA not be very wide of t>;he ltruth il-l fsppoflng, that-the- I?tarldard dita1 rod, whicho 1ay cloSed;: up in- i-ts cheltX ellder the ganopy Qil Ibunivbileath>; would fuSt; the fame-fort of altertlate ex?anfion alld? contraSon with the - above-mentioned; 1ax1k; t-tiat is; to fay0, being of REa wood, its mean expan*-

.

fio}l about the tniddle of the day would 1)e j b2050O 6Bf a-n s--nch, By this gantity theni we; muR augment the adimal obServe;ds expanSion of t;he meafursug ;rosh,: i-n order to;0obmin withitla certaii- pr-obable- liinlts (fInce we cala-ot determille it accuratelyif the equatiotl for the expNanfim; or that fpace by which the apparent mcafurement.7 given by the x37o- deal rods {hould be- augmellted in olda to obtain the true length Qf the baSe; oru that which would have been given by unalterable rodsX of thef fame origiIlal length with thofc of dcal> asoexprclid in. th bllowillS tabl>



w- j- l, -w- - 8 | t f

41 TAble o-f the Expanflon of the Deal Rods 0 X s f : . . 0 . :

: N° of EIour of . Ternp. C)bServ- Deci E4uation Equa-t;on Total j iDays.. rods comparifon-of the ed ext mal for the for the: expan-- 0 meaf. Sj aar. pantioa. mean. meaf.rods fiandard.- flon.

. . *

h 8 7 o In. In. - 1n. 0 In.

5 { 6 oP M 62 } o } QOIO 1,050 0.2625 1@3I25

1 17' 195{ 6 orM - } To } OO10| I.950 o.487s '2.437s ;;r 23 24Q t 6 oP M S4 } Xa } 0a021 5*040 o.6000 .5.6400

7 30k.M. 6 l 2.Iis 1

24 27° IX X 5A.M. 66: wr o.O33 8O9 1O | o6650 9*5750 5 45P*M. 64 WIW § §.

tl°|. 2 27o 4 7 oP A/I 67t 0 } OOI25 3@375 t o.66S0 4 0400

3 290 t 7 oP M 575 } @w0 } 0.017 o.493 0*j250 - 1.2180 _ _ #

j Total 1370 - - _ _ _ _ - 20*8 I8 3.405 2 4u223 . . . .

; * A aa

N. B. Although the rods were not compared with the fiandard on the I6th of July) yet tl.le expanElon probably was, and therefore has been eRimated at

R the fame rate as it was found on the fullowing day.

* v w > , W w

Nevrerfer tiv I34f on Ho;unMolrtHeatli. 437

By examitli2zg the preceding tableS it will ap?ear, tilat tll-e total expanfion on the T370 deal rodsX including the fmall equatiotl for the lengtheniIlg of the Itandarcl, atuoullts to 24.223 inches, or z.oz feet; which beitlg added to the appau rent lerlgth of the 13a-fe 17404.3I feet fortnerly obtainedX we ;lEall have, for the hypothellufal letzgths 27406@33 fee-t: and frorn this dedtlding o.o7 foot, the tscefs of the hrpothenufial above the bafe lille, or the reduAioll colltained in the fesrenth colllmn of th-e getleral table of the baCe, there-will remairl 27406.z6 for thediItaxlce givell Sby the deal rods, between the

' cellters



438 Hayor-Genesal; Rozrts Acount of tbeS CtllttrS of the pipes terminatillg the baSe, reduced to the levetS of the loweRy or that at LIamptotl Poor-houSe, in the tempe ratvre of 63°, beotlg that of the Xorafs fcale mrhen the lerlgths of tile deal rods were lai:d oS. All thiSX however, IixppoSsz three thillgs to be abSolutel-y cer-taill: firR, that the expanfox of tlle rods has been accurately cIlimated*; fecotld-> t-hat no

error has arifell ffioln the butting of the mds agailaR eaGhi other ilu order to bring them inrto collstaEt, and,* thirdly, that:* no miIlake of ally kitld has fbeell committed in the execution. Wllen we c-ome -tOs give the tree length of tPles liaiv as ul-ti tuately afcertaitled ly mea+Xls of the glaSs rodsX it uril'l appear^ thatolae or more ofthefe threc- haue aflcually t.Xken place;. although it is moRX plobable, that oElly the tw-o firSt fi(3urces de

terror have contribtlted thcir Chare of the total diSerence be-- tween the two refults. But tlae difEufElon O>f ttlis point mu{E be ¢Referred for l:l!ae prefeiltw, and I ffiall now finiffi thc fu!jeEt of tlle expallIRor} of the deal- red-s, by StiltiOllitZg two other- cornpariSons of them, -whlch Serve to «ew7 ft'ilt mot obvitunyF

holar impropet they are for very accurate mearuremetlt ! It has already t3eeIl remalaliedX that the lall week of July

Was rov;;et aS to occaflon a t:ota1 fufpenfion of the operatiolzooma XIounfosr-Eleatha Q;< the z6th of t1zat molltllX at 8 h. A 1!de tIae temperature being tlkcn 63°, the rods were compared svithb tile andard alld iound to exceed ;t/ at a medium, one-fifteetlth part o£ an inch ilStow i-f ure fuppofe the s^rhole bafe to have. been £neafufedz s^7ith the redsr in tllat ateg the dlfferetlce would -bave amounted to En£?re thatl 72 feet9 excwluflv:e of wh-at the ITandard itfelf might hav-e alteled froxn its originaltlell;th.

The other coznlrarifol ^7as ma.de at Sprizg;-Groveg in the beg-inllizg pf Selptem:7berg after aur operations on the heath had bee finithed7 andf the deal rods witll th$ir apparatlls depofited

7 s3nd¢ga



Jiaretnen if >-v B/es stw+*TlounnowHeafho +39 nderwthe roof of Sir JOSEPH B;ANKS9S Barll. The o}jedc- hei:t

;4xn itiest vas the-meafurement of fuch a fpace as athe garde0n; wouild colaveniently admit of wEien t-he ro7ds were ill theil dry -or contraAed ftate; and to re-mearure-the fame fpace-next morning svheol tthe rods, being left out for tIze purpofe7 had imbibed 11 the humidity they -cotlld from the tnOifture of the Alnterverling night. According3yS Jthe fourCth beirlg a<fine dry day, tlle fun ffiitling bright, and the thermornerer about 68° vieventeerl Rands xvere arrallged in the 10I1g walks with fosmu nicety in- the fame inclined platle as to appear btlt like otleW lohe firR or lowermoR flcarld had a brafs cock Screwed; to Hit$ topv Thetwo uppermolE, r:ha isXto -, tEwe:fixteenthfa;0: ^feventeenthX avere -of -the fixed kitidv each fWith a bra-fh flide snd placed only forty-five itlches afunder. The firft deal rod was made to butt agaillR the bIafs cock, and the reR fucceS fively againI} each other, ulltil fiffeetl frod lellgtlis wtere mea fured of, alld a fine lule drawwn on tlae flide mar:liing the extrv mity of the fifkeentTl. That-rod betag removed forty-five snches, taken from the braSs iRcale, were then laid oS 13acl wards from the line on the nide of the lieventeenth to the nide Sof the tfisteellth Ilalld where allother fiDe lille was drawna

. .

Thus the fpace comprelaerided betvveetl thts laR lille atld the cock Aon th;e firft hndX vas juf 3Oo feet, or fiEtten coinetdeti--t rods. -Duritlg tO Digtlt of the 4tll, which was vey hne, the+rod$ -lay etl--the fmooth grafs. Al3out ftlll-riErg of sthe $:*h there

*4naine otl aD thick ig wZhich entirely diMpdled about 8 o'clockO fKt 7 h. A.M. the reds being lifted £roLn the gr-afI:¢ it sras peF >>ceivedS that tht under iides vele t.perfeEtly dry, while a11 t11e wreR was qXlte wet sv-t-th ;the dew that l1ad Sllett. rlle fotlr- teen fiands3comlzrehended betweell the ErR and fix*teet<tI-l, >iGllavitlgtheirudiftancesgr;adually reduced fiSon tv=W;Ct1 feet tEliee

V^.tf LSSVo M-1m m -oncht



44O mfo-*Gens vZ Ro9Sv 3soant of +Z17e JiAGhes to tWetlty ieets tlle opeliation of rewmeafurementswas tShen begun, I)y placitaG;; the rods in coitlcidence xvith eack; other twhich xv.as llOW found to be eafHy;and accuratcly eieAed bgt a fetfw repeated Rrokes svitll a wooden xsredgeo only) until the itgell rod letlgtils were meafur+td ofEfi and t-fitie lille, cor refipondil jgo with the ivory c>tl the fifteent-h, vv:as d;XaWIl .on the braii flide This litze was foud- to be o 4^o9T$T r.trillegrehalf al.i

inch bey4nd tha-t whlch tertnitzated:^Xthe-3Oo fect. thei preccding; eyen-illg. . H¢tlce it.. is;^...es7idellty th-at t.he dew...imbibed :oulyAil;. e luight, or a i:pa.cq of tzang notrexc<ding fion!rteen hourss occafiolle;d fu£h all expanfior>+in tlt dealarods,. aaain the whok-- bafie wQ<uld have amo.urlted tQ 45.484 inchesO S

It is fuSicietltlzt abviousy that th>;.>la0o;menti<3tl.ed ¢xperis

3Xent-.wBs-lnore a.C.qu.rate9 ............... Xa th: proporbon o3Fsabout fiitslitcx

we, than- avy compa:rzfotl w¢ could at that time have madc witli the Randardt Bt. fince @rnediatelyS t¢E it..S..S.Cll.., bthe fun Wlolle out.very larlghX ¢t-t; is by ;no m¢ans cgrtaitls how foots; the rods would .agairs havc cottraAed to thetK forrrler lerlgthg o-r 3zear its had they bQell expofed !to tiS. rays. P@p¢ated compa rlSons for. af>ert;aling faAs- of this SQrt9 ;.at. very Ihorlt;Ysilterims, axe abfolll£ely itl<ompatible witia ;!the. nature of i fuch tedious and troublefonn$ operatiotls a$ th; mga,furetlt of long bafes* aIad here, illdeed, 1X-es the great objedion to the uN; of deal rods9 that at no.timci can Xw>¢ bx certain h:ow foow-> after a comparifonS ha$ been madeX they mayralter their length in a.proportions andt fometixnes toQ evelu il; a fQllfex diffk¢at9 from wh.at wask e2w pitedo

tt"...



ge#vrintnt- ¢f a SSHe OtX tt3wnOW* ath.

t3icripzzan f thcGlWs Rod Xsgenly azadu fie f-toerv t-ne;the length: ff tf:e- BJe. 0 tb. iXt,

It has been i]Lrdy--meIitsoned,9thati tXhe w-Wk of ray srea ther in the end of<>July was entployed iws provLding the glhlk tllbess alud in tiollcertit3g tSters with Mr. RAMSDEN, rYHltiVei4

th-eir cotwIl-rud:ion;as meafuroIlg rods. Mtwithtta£leing tlleir great length9 theyx wtre fioullds t- Al)e zfo''Rraiglat- tlla:tg aYhen laidi

on a-table9 ithe te9 I?lacedratt-iae tadilmking-tEroEh them§ could fee;atfy XEmall eleje&-int the- a^xis lef the bore <-at the other cnde

The-nftte<and c6tifirud-;otl of the glafi todsb wherf ree were 4ininledd-ior the dperataon, will 12 beA concejved bys tonfideritigt with carei<ald attention the plans iatld elevaions tf<;them,;; sn oleror m part, to diiretltt-Scales ill t* MIX.\ owire Iik-evtife m-say -be feell, platlsiatld SeEtionrs- of xtle alds of the tul3esS tts;-their realditizentions; -for8thebeterutlderRandi;it

et$he: --feveril- pa-rtstf3-4;t:k avr-atos placed<-'thereil*

The tai colluitlfTxg8 ahe;tulje, and -th-ch > vErves ;--to keep it £iom betldointin>>Nots ortginal;Rralght potiotl, t-is every where ot the de-pth of eight illclles9 of the fame width- +( -in * the midSdlefi, alid tapers 7fiorn - > thence-, t-in -< Ncurt-oltilear mazine-ry Lt towards each 6nd, whereKit os oti--^twoginc-Iles anfd a -q-iiirter lroad. It ts xnade bf c-lean kiite deS-s<-tvhe ktsFo -fides lleiii>^g t hatlf all Sinch;

and thertop atld bottom tllreet-eigllths in-/thkknefsv TheS laI} are placed i grooveP{itta b recee thert, aboizt half au Xtlchifrom;the topper ai- lower->edges of-the fide;s whxcll ljetld

ttlgo eafiAy, alld applptTHg clofely, are -Xthen ;ifirluly -fiRened by SWQ routs of woodf-ficresvs on each fides - to t-lje> top --a-n-d bottan

-m rll x- XCf-p-e,



+-+ 1X1or-GenerulRoY9s 24cvount of tbe reSpeEtively. Thusy tlle depth of the fides in oIle fellfe, atlS 8ie fpring whichB they haveby bendilzg in the other ad asn truSes, prevellt -the cafe frotn warpiIz:g atld- render2; it fufS ¢ielltly firoIlg-, aIthotlgh at thc fatne time,. confiderillg its great

Iellgth, very light. Th-e plall.of tlle lmiddle rod reprefetlts the cafe with tlae top

oR, that the tuSe may be feen placed tlz!ertitl :- tEle right alld Ieft-lland rods liave ttie tops ony wheireby may be feetl tTie ovalwopenillgbiil the middle-ofeacEi\utby amahoganylid; and alfo the pofitions of tbe turo thermometers, with: tubes bellt at right-angles, fo as to place the Eball about two irlches downwards within the cafe-, ior the berter -aScertailling-- the temperattlreE of thie g;laIvs>, as w-illaeafily be cotlcetved by conE1; deritlg the re?reSentatits of tlae tube atlds biall in the fieEt*1o acroSs the middLe of the rod.

It is to be obCerved, that the middle of the tul)e ls made falE to the middle of the cafe i-tl the foliowitlg tnantzer. FirIl, around the. ddl-e o£ the tube, a qUatltity of pack-thread, imZ merfed 1ln liqu;d oglue s>< was wound by Several rreturns on<; itSelffi for the fppce of about two lllches itl lengSh; and tU.I1 this maSs of p?ck-tllread,^vutiille the glut was warm, a ltrongmau hogany cc)llar was forced, whereby the threefubRatlces became fo perfedty united to eaciotherf that they might I)e cotxfidered: as one only. -AcroIi the bottom of-the cafe ill thewinfide,< three mahogatly braces- C gelrdetrs owe in thEe middle, and olle: half-way between ^ it and each end,2 .are fitRened, bys meatls of krewsX to the 1hiotr-o;n} arldbfidesO. Thefe rlIB about 1^ incE tbove the bottom, I>o as t-o place the axisl of the:tuSe . when ;a - ufe> about Z x llaches above tlie fuKrfacerof the RCincis on whicK it reRs. Le end-pieces of tahe caIi are likewiIP of mahoganya,> xbout X w illcli thick. Eachi cctufills of two -partsn a lower atld an

upper-



MgnJ>^e2e>t of a BafFe on Houolitlow-EIeath. 44g -tper. In the lower parts, as well as in the crofs bracess there are Semi-circular cavities lilled with broadclotlzs fitted to rer ceive tlae diameter of the tuSe, whicoh: reRs vin thern, and i-s confequently fupported at Eve diEerellt poitlts. The uppel4 end-pieces, havinglikesvife femiecircularcavitiesfitted toem- brace the upper part of tte tube, {lip down upon it, whell it has been, by repeated trials, brought to-its true pOfition- that is to fay, the axis of the bore iIlto the fame flraight lines the cafe being all the svhile fupported by its extremities oll tssro

. .

Ilands onlyl in the nzantler: in which the ro-ds are applied in aAual meafuretnent TIle braces withitNl the;caSeShal7e alSo their upper pieces, whichy in- lilie marlller,: apply clofely to the tubeX alld are hxed to the losver ones ly meaiis of fcrews. Tlae svhole together ferve ollly as Rays to keep the tube irl its

true pSlace from Ihaking; but without bitadMii,: it however too cloSely. Laly, tlae mahogally collar glued to the pack-thread on the middIe of the tube, being firongly fixed by four fcrews £o the middle brace, as-may; be feen iil the feEtion, is that by which the tube is kept perEed:Scly itnmoveal)le with refpeA to the micidle of the cafe-; while it is uncotlfined lotagitudinally in the cavities Iined with broad-cloth every where elS*e.

Botll ends of tha tube are ground perfeEtly Emooth, alld truly at right-angIes to the axis of - tllebore. P - That e-tzX wlaicll u meafuring ufually iies towards the Ieft-hand (fince InoR

people zvill work the fcrew with -tlle right) projeEs - about fevententtis of-atl inch withorlt the caSe>;and is-called the hed elad, becau-fe the apparatus belonging to it is fixed. - The eher end; towards the right-hand projeds about llinertenths of an inch andJj haviug a moveabIe apparatusx kis called tha

. . .

1 t!F '

vea 31e eIlQ- t



+++ Major*CenetAl Rots XCCOU Og: bi;

-lthe fixed apparat:us -CQ6IRS of a c abovtthree itYches<4-t 1C1lgtiz madc oiS the srery beR Ix3ater!ial9 and fo llicely Stted to -7the bolFe as pR to adln;t of bewag forced into t;thout burIting -tt l;X-w the middle of;the corrk a cylindrical brafs tube is placed, ss}lc>-fe fides are thiny the waward etod tthick, atld the outward

tnd opetlO Itt receives a Reel ptn, whofevinward etld being

formed itto t -fcrew} is thelelty f Fxed -rinto the -thtck- metal of

*<the tubev The -Reel pitl-->rries outwardly a bu-ttoll and twec-ld of bell-rnetal. The neck fit--s :{Q <very C1Q21Y ;IIC open end d- the brafs- t:ube -as to prevent any llzakevl^tlnere, -at the -falne tsm!e- that *-tlae inElde of tlle Jauttof-l applieFs-very jmfEly tC3 the g;roulA end of th-e glaSs tulze, -to whith the outward iface (being;

;a- true plalle)-i-s exaftltr panallUl

-The moveable apparatus <onfiRs, like the ot-her, of a coR

wnd; brars tulJe of the faine 1e1l2;t--ll.- Before tlue infert:ion of this

-cork, an ovlolzg piecebfbten-1t-enths of a--ti itlch? lorg, aWd twov

tellths btoadX Jwas ctt fRom -it}-infthat Sart -65 wts cylinider anZ

tweritlg -to theE upper par-t of« the outward fen-d ;of the glafs tube}

ot1 the>inwarE;l fu-rface of wllichs abut half an titlch from the

tdS a fille litle haed lDeen previoMy-cut by a diatotld poitt. The braSs t-ul;)e irl---this;cork>coIltain$ w-thin eit! a -loofe Reel xvorm, ori helical ;-fprillgX t-forteth-ing lefs .than - the !nterior dia meter-offthe tule>. Along-t.he-cawty formed jly-the iiiral) therepaflesafReel pinX like 0thaft;Ar3L 1the-fixiexld; t3ut it is; longerS a-nci has -ne fcrow at the i.award end, that-;lDeingVnicel5t- grou:tld Co as--to fitsz circular hole in the+-irlward end of ti

;brai:s t4ube, sthile a trxatlegular bell-metal "-tledk fits;>iane of that

figure in,-thewtoutetard eM. >thus tIlelpta moves :fxely bac3>

wasrds or --irwaralts sritiLout -any fiakes otldr>preffies won the

lleel fpring; by mea1ns of .a circular brafs collar, placed for the

urpolie,-v-¢at the ilward ond of the ta@Ck-t whlle:S-the-outwad-

5 tad1



^m of . Hr onk H-ovl-ffit. + /

eM -$ ateached to a bell metal btl)ttotlw The outward titSce of \ . .

this mov¢able buttx is @herical, deRibed on a ra-dfus fof about two1 inclles ̂ - >thile the nuwlard iI;lriace lilte tllat at tho Sed e-ttlds woul-d:apply clUly- b tlle grout;ad- ensd of0tithe glafd tuleX but {ht3uld - twor be pued b.far irwtaRd as to touch it --A circle aud tla-rrour Xi.&67 cut;fir-â Sofid cyItub><of ivory; fitted orgl-nalJy to etuter cafi-?ly the glfit tubef is attaclaed to t-h¢ nfide of; the buttoll.by; ftna1-)1. <s-cresvs> and- permin the nr<32 ta

pafi ttllXOU« allole Ina-de ofw tpw in-;the ciml-e. The fiivde xs about eight-tenths- of -atl iLsch: lo^lg,; and Shas -a i<e Intrf-ec- ttOR Ctlt tXpOIl it 1WM 6t 0 iAwa;telldss; . X tkCk .tO ieNdC¢t X a more conEp^wuous*> 'rtiu-%¢ t-o md§Xil^ng bg-h-t irwto con-tadg and the fised;button-o£ oneXb<;pxScI-agattl-It the -moveatzle button .iRthcothe> th¢ mrfEl,oll:is êr :pued- for xvagrdsW until-itcoillcide$>with the diamond§IineUotl tl¢t'!illterit'

. ,> , .

furEane Q;r t-he tube-}- fwh SeCllg ioVb a4uRed7 asthcaty wlle2w £he coincadetlce is- perE&, vthe kliXuce l)etwecaL the plane fur- ice.o£ one.lbu."ol.ffi.vaIad;th&[email protected] of tl-e. othel* is

esaAlyst;zzellty;feet. The liefthailEde of-the plat repre- fents the relative -pMaoll- ;of the: vextrem-lties of the- fir-hc - alltd

f . .

iSecond tS, whelw: tlae ivoryte is in coiiacidellce wit:h the dia mond li^ne. And ti xlghtWhat & fide iBews e relative fitua tSns Of the etemities: of the fcealld a-nd ffiirdvrods,^ beire the ivory.i-s brougli-t to ceinciNce with- theWdiamorad li;le, t-the iNde b&}igStben; pplt3td ¢mt w the adIon of t-he fpigal irin$ withil} th.eCcork-4*!-

.

Eve tod**hase four; ieelss two at each end.: TSey ars two.

-Xinches Iod}am¢ter..aildv-col}neeed.>.lzy.a common Ree....axlsE

.

-Whic-hsrrifes.ansi falls-in a vaceity prepartd.for its admiS;on^-iiws thg maho3gany; eJ-dîec"X;- the usld.t jar£<sf whd ^7actity is ahrv.ards fil.ld..wkAw

A bmi t



4+6 or-(7eneral RoYss S¢count f t

A brafs firap or bridlej, about eight"tellths of an inch broad uaR es over the top of the-caSe,0- and defcending dovvn each fides, bendsi-outrrards fo as to tozia; a projedioll for the reception of the vitheels, nvhoIS pivots tWRLl"'it'lg but llear to the lower end of the <ridles svhich is kept in its place by mealls of the two ilde Screws workitlg ia grooves, atid; tile miLledheaded fcrew at top, Thi-s lai;t ferves like.wiXto raifc or depreEsf the wheels at pleafure.

Each rod has tsve cvefi fect placed imtnediately behind their- refpeEive pair o f sshec!s,; cxtendin8; outwards -about 4t illches from lthe center 011 each fide. Utldor their outward- ex tremities, finall pieAces of harde-lwed Reel fe3rmed into the teeth of a fi le, are fixed- by means i-of krews. W;hen- the hr: rod has been laid in its true place, by ullfcrewitlg-the tnilled headsD the xvheel-s arei fufired to rilE, whereby the whol- veight is lemoved-from them, and throwxl:upon tthe tecth of the files,, which then inWdent themSelves: into the furface of the Ratld, and loecomeasfit were united £o it. BUt WE1en the fised bUttOn Of the FeCOnd rOd iS {31OUght 0 PRefS agail1LT theD 1nONYeabIe BU£- 011 Of the firS, the WeighT lteing then throwtl UpOll thR 5Vhee1S bS SCUeWi-1Rg the mi11ed hCadS at tOP,0 Xthe rOd iS efi11 11zWed On bY t}l& i110NN i1Lg SPPAratUS. - X :- - -

The tl1ree rOdS aRe rRU1nbOredX SS Were thOSe OF(ICa1S l .4 ; 3.4 , 5.6* OII the firI} Or Odd end Of eACh rOd I. 3. aIRd 5 tEl1Cre ItandS a braIi fork, about two millches high 5xed lzy fiour fcrews:atad at olzlong plate t3 the t-op of the caSe. On vlae Second or e.ven erld of eachX 2 4 . and 6e there Ilallds a braSs p-llar oiS tEle- fame height witll the fork, likewlIE fixed to theh top of t:he cxSe Iy four fcreurs and a circular pllte. Two ficels rods o-r hooks were indiflSerently uSed for brirlgingS up-the moveable rod (the weibht tliXJlying 0t1 tllc whecls) ato its trz pl-ace. Th>y

.are



&7gaj6aresent oJC a 2roJ<e os lHoulilow-lHeath. 4t7

6Ere bOtil reprefented ill the plate and --etlly diEer frore each otller ili;theXfhape of-ithe brafi milledgheaaed nutts

-ellat-woR uforu the @ewX 05 il-50Ut724 illches titl lEllg-tl1s

into which the rtlght-hawd; elzd of eacli heok is fo3rme61* Thus, hwhile the l-zut enters very Slêely -itto and ltefl:s UpOtl-s

the fork, the left-hand end of the laeek has a-}circular hole itz eits svherelyy st Xaps eafily off and ot1 of th!e braSs lllar. ]3y -referritlg to- the ...plate.9 lt will -appear veIsAyv obvou-Ss from tlle nature of tlae nut on;;the leEfi-haI;lCI lzo* tilatFltit could only ulove ttle rod-on to-coincidence9 a11d could not 5filig it back- sagain, if-the bufiwefs ;>h app-ened- at any tlme to be overdo t1 e rin whichbcaSe-it mtazs IleceSary b fmove tlae S a elIt-tle back** wards by the hand, and thet} to work at-l-es withwthe-tluts, mtltil the coincHetlce was -aceurate: whereas the nut on the right-hand hook, havig tsro {houlders, could;6etther punl or -<pull the rod forwards or backwards: atld although tlai$ ap peared to be a-rl;advatstage yet itfwas --fbutzid fio-m- expeîelz¢ that it nther beund the h-ook too mucll, and occafionedSa kitld --of fpring ill -the parts, which -foluttimes diRurSed the COitl0

cidence oIz the rernoval of the-hoi; wilereSore t was often ap ?lied, like the otheri, by ]31acillg the Scre;t itSeIf tn ithe>foiX -and worlitlg witll both Ilzoulders of the nut belaxnd it.

The pofl-tians of tlle thermomDettiss atld rnahogany oval;li;d -on the top-of-tllekcaSe, have al-ready beell tnentiolled. qffhis >1aR, beiIlg utllocked alld rem<3vedy permtts the -cafe to be:Iooked oato9 or the hand to ibe adrnitted9 itl order to lJe centitl that the faRerwings remaitl Isfe atld elzzire in theiitlfideO BlXafs capss xvitll the- refpedive tlumber o-f tlae rods engraved otl tthemg are likewite fcresved -OI-]L Sthe maleÎScrrs itl the etlds of rthe cafew {tthrough which;.the extremitles of the- tubes prpjeEt:, to;pr-C

ferve them from accidents svhen ndt ill ufe0 ̂ -AIl£1, la0;1yX to ^voL.<LXS\r-. 1S n tz fireng;thcn



4+^91 mfor*GeaervI Ro§§ Sccott of tb - Arttlgtlzetl*-the cafesS bilt more pajrticulally to prevent ffiea. hm being rent when lollg expofed to the flll's rays in thc field, th& f1des.are covered with vbrowll; lkllxn lai-&& ollJverf

I moothly+ atld carefully glued withrtllin glu4; ufed as a flronger lrind :oif^ paIleX to which it rnay vyE bq at7ceSary to add a coat O£; aiL' pAilllo

:E:ach of the gla{k -rodi^!icompleted in thefimanner^-above g mentionedS sveighst about ifi-stt;-one pounds Their lengthss were aCcertaneds by; tneatls of t:w¢vebrasii poirwvts placed in the great p1ankS the fpages of Sty inchesglDelug lakd oS- withz tht utmoR careS from thFe btafisefcaleS xsthen the tcmpera>r$ of walle -3d 4 lZZAilled fOr tht gCatCr pzt Of tWO id& (A-llgUa T St-+

at¢dWl6th) Xat-or very llear >68°^ 0Ft ;.this purpoSe two braIX >Etangvllar cockss whofx aItoertlate furfaces had been previouilye ground tOmtlg wgre o plged- upon tEle plank tfbt as tobifedck the extl¢elne dotts ;. in whicTu -;0fituattioll r t}ley xpreinte.d to each other furfaces that were truly parallel The rods l:)eitlg thelu feve^ rally plaxed between the cocks ** (orr a«s svas foutl.d to lQea letterX

. .. * s. .

method,

e Tlie firfl of thefe cocXiisg- or that to whxcli the fxed button was applied -Iwadb4> a hole in it csaAly of the height of the center of tlue .bllttotz? and la*ge tuoz1gh-;g 4:e permit the point. o£ t-he inicrvmeterrfc.re.m -to pafi th>ugh -3lt the. :id krw, beiggfixed on the fatther fide> os beyolld the gock. Z ThlXsf wiwxle^tle tempera ̂ ture- contintljed. accurately at 683s the <;fiveXd !3utton, or ally othelt plalze irhce} bcing brougllt n9.to the hole in the cock, and the mictorneter pOiat fc.rewed B

51' 35 ;ll0 to touch- it, the celncidence eontinullag tn--the lltetwim peiIie ti ex-a%

diRance Qf tS\teNty @et W3s« obtfai-t1Cd- between t1le-.po-nt of4.the.X;ew and t=hw fecond cock ;z> af which time ti1e+d1vilion arlfavering to the xnde$ onv the head of tha mxcrometer was carefully nott*4,5. This being dotleX the ceek with the h.ole was re^aloAv.ed Fonz the plank arld thevrod;Rne*c feverally adjuRed by being placed betsveen tlle poirlt of -t;he icrew and the fecnd cock. Thi-s ftzblitti(n of the micremeter po,llt} sinllead of t<nt; St*1t ctck} -was f-oun-d neceStry; beCefzeltiv dllr.-inb the ope3ratt0n of ad3uRtncut? thc tctali?Crature vnrotlld++b4.lctXimes charsS, a degree

genqall;



MraHureS@#/ 0 4 BaMe on Hounflow-HeatI +4q method7 betweell the point of a micromerer i:crew fupplytg the place of the firit coclra sand the fecotld) tEle ivory interfedio- was at firA weceS!arily carried beyond the dialnoncl lille fo as to tnake the illtermediate Epace lefs t}Xan it Ihould be, until by-the gradual gritldrlg dosvtl of ithe movable lellrnetal buttowX it was enlarged to twenty fbet as then thewn -by the accura£e

coinciEleilce of the-interfedion with the diamolld-line. It was by theSe diRances in tTle grearplank proleng,ed %

twet-ty-five feetX that the new length of the ITeel chain wa$

now fettIed, fo as to obtaitl ;tlle ftllleolle hundred feet at four mearurements. At this trne too, bSraIi points- were irwtrotJuced into the chain at every twenty-five sfeet vwherel3y its exteIlt -may be cotnpaled on any future occafioll; lJut the temperature had 210w f;lletl t;o G6°;-o

Dl;430/*tion- f tZJe Szazzds fior the dot mre^meezt w;th zk sChain and Clvfis Rods; dfcriptinn of the vSparvtas tJhen;appAed xo the ends of i the Chaie; and vItatnare contingation of tbe ,sea0areznent wifh the Gl4Jns 12is aI;Z&e. Tab. XVII. at1d XIS,

From the vai*1ous clrcutnIlances already :netltioned, ill tht courfe of this tedious, yet tlecelIary- recitaIX it had been for.a conirlderable.rpace of time fortieelzX tIcat tile ;refult giverl by the meafuremerlt w itll thz deal rod s mu R be ellti rely rejedved s generally irt exceSs, fioznillandling the infirumetlts. Qne degree of alterationj, prodllci-ng a;diSerencef of about R5Ith part of axl inch In the twenty icta was very eafily-and accurately allowed for by fi}cn a micrometer as this; svhictl <essXed

the coitlcidence of the ivory itltelfeEtion with the diamend line totbe gnore or lejs perfeEt, when the Ilead of the fcrew wao .rnoved tWQ diviSons} that is to faAra Xv-E;ths- <? :vth p3.I't Qf dLi inck

NnI- Z D

al-ld



+;o<#> eorw(7eteral hy.§'St Acgat ft.*'4¢

atad that- by the gla:X rO<ds adllered tQ as ;every wAyX de-{irt;-ng

o;f-the- prefieeretuce3 lWauSe of the obvious imI3rOpriety thesre wouDldDbeis in takitzg aKmean bet-vveen OLt iSdifpUtlblty gOOd

atzdanotherleiX peri& Elosvever Imall-or- trifltg it-leality tkle' d;fferetlee ofC thye two tnighthrultit¢1y;be fomid; Otl-* a

suinute alld Ibfupu10ts cotuparikn.-- In order, ther4o$¢7 * to fav!oid any repetiti¢n of tW operatioIl

with the glafs rods) alld at the mffl t-tkme to ¢;gve Dfomethitlg like a fiir trial to the cl<ain,.itS was proHdXl tha$-;<a double tneafuremetlt fllbuld be carrled-oll ;wltwh 13oth at- conw, that is to Ihy, t1Rat thoX numlJer of RaI}dsS, a>d-ifev-erctl -totSher -parts of

tlae apparatus, Ihould zbe; So fat agmented as .to admlt the clwain to be- pked -etwiw in aNanc¢> aM then the rods.to fol low in fucxeE1on Otl.the fame; Ra-;Xads. A!ecorditaglya thtwriou$ articleNs^>having been fent-!lto: vlaeslzarth-weIl^-elad of the 13aiTe onL the everli-tlg of- the ;l 7th of A^iguR- the operatzonv of t;hx dou*; lxle mea:furcment co-mlmmced-xaatPmorning £l3;e-X3rth

By refirring to tab/.- w XV1T. it -Wlllr bs f9en, V that- sSventee Ilatlds were lzeceSary for fupporting the chatt> the; app;aratus attached to eacIl end of it9 ..atbd ten-,^coSs vllerS every five-- :made about n1nety-eght>;feetg ill order tthat zone length of the thain beiIlg- meafured - oF- in tlle firR -fiv7e: it imightR be drawll

. . .. .

5iWArd illtO tht l fiw, alld Sfo onf Thek feventen Rands; were difpofedscof inqthree gfotlps of t-h-ree each;;atld four lintelu mcdiat¢> between . the cetltra3;! aIld ext.rcme groups The midt rllea or nlde R-aud of eacll greup-W(itdiRinguinled becauSe fome-; of theln hiad:SUrSs- {ligles on their top) fupported the handle of the. chaitl atldi of courSc received the trac:es madx at; th;e feather eclged pieces- of braIi, termtuzatilzg- the bcg:ijuningt alalfd endingb o£T t-Ie-l<undred feet. Thus, theve wele in all- fix ITatlds,- inter-

,lediate tQw lthogoe. in ,<t thx G¢Llt¢S sOIc seElC group that fspported

y the- tS.



Me f re>X¢Xz of a Bv oa Hounflosv*Heath 4 St thie llltattytight feet of coSerings 5^rhich svas kept fo rnuch flsort -of the- hutwdred £eer, thatin extreme parts mi;ht not refl: UpOllx or even tov-cl<> the>Wtaral Ratks. To that on the leEt iQf

the centerS was attached theapparatus for -the firLtor zeroetld of the cllain ;- atld to tlaat :ori the right of t:he cetlter was atrached the apparatus for tlae- 1ak - end->- of the chain W hen - the -fecolld; cI;lain=lEerlgtla Xhad Wen meafiuredoff; the firSt--and fixtti of the £ofEer ltalads of tlre lSIR- chan were moved forward to prepare

. ,

br the tlli}nd- chaill ; -an-d tlle four remainitlg coffer Rands were raifedX ulltll their.Xrfices calmle illto ttie Iime plam with theX {lide Ilatldsi; for the re;ception of tho glaIbe rods. . - The Ibace by svhi£h thefe Itands were raiISed was- abollt three ir^ches ;- for 19 mucll -;llig,her was the X-rface of the l!tlterible-or <flooring; of tIze coirs thany tlle Itands.which Xpported them.

The apparatus attached to tlae firrt endt of tEle cllain or that whch fervedC t- pulI- it --bacld to the polnt - of commencrement; while a weightlcontinued I;Sfpended- at the -farther erld con- fiRs of two partss as may be- feen by referrillgz to lEhe lefi-hand: fide of tal3. XVISI. lI^r->3 a fimall wooden fiime7 fitted to {lip o11 to the top of-anvy-one of-the orditlary Ila-nds7- placed immeZ diately to th@ left of that which fupport$ the hatadle. z Sec on;dly a flat Reel rod, about two ftet in 3Length; wherein a Ilumber of holes are pierced, about ;all trwoh afunder7 for the recepr}on of; ae Reel- pin placed in one of the holes+ as beA fiuits-<it diRance of the Rand from*the harudIe That end of y the fl:eel rod n-eareI} to the etld of the cha-in is formed into a--- Screw about; fbur inches in length-, arud itt teceives upon its a f89 hook- Etted to lay hold;of the IRraight part of the ha-ndle of the -chaino Within the forked hook there works-a lErollg milled-headed braS$- nut which adring upon the botbm of the forkS the chalu; isthereboy pulled baclrj until the wsrc IizUendi-tg -e plummet-

.



452 ..orrGeneral R.os Sceoanz f tbe .Ercorn the dare QA tlae featiler-edge coin cedes with the pOillt Of

gorulmellcement on the ground undertleath for which purpoS there is a liole in the top of the Itand throug,h which the wire paXes. Tlle appaatusRand, thus ferving to pull back the thai, was cotntuotlly loaded svith doul)le weights, placed or tlle two hindertnoR legs

Tlle apparatus for the laR elld of the cizain confifEs like tile tiormer of a -ftuall wtooderl frame that can be readily nipped upon atly of the common ftandsX as may be feewla by referritlg to the rigllt-laalld llde of tab. XVII. This framet carries a pulleyX over hicll a lope paIles having Surteen poulads weight fufpeladed at otle end of it? while a forlied-tlron hook at the other end lays hold of the fl:raight part of the braiSs handle. By xnealls of thefe two appa1âtufies the chain is alsrays kept to the fame degree of texwEion in its coffers, iti each of wilich a therZ mometex svas placed to itldicate tlle temperature; the whole Cbeing covered up from the direSc rays of tlle fun by a narrovw pieceof litlen clotll ilretched tarlot%>it fiomw one?end to the other

. . . .

iEach coSer confiRed of three boards about hal f an illCi

tlwickj The fides weiê alDout five inches deepX ilailed at the .

-middle to an interfole bottbtn of four ;tlches, itl fuch matlner as to ie reprefetlted in feAiot) by tlhe letter H. They svere ilL .made, beillg by tlleir parallelogram Ilzape apt tc) warpS which migllt have been prelletlted by giV;tAg theal the figure of the cafes of the g;lafs rods, that is to fay, tnakilzg theln &vide in the tniddle atld lwarrow at each etld.

We are t1OW to proceed to give fome account of the doutjle meafu;êment with the chaiLl arlcl glaSs rods s wheloeitl it nauR be rememl)eredn as alfo ill coIltinuillg tlle operatiotl s<s7ith tTle glaSs ods aloae, that itl referotlg to the tnap for the daily progrefs t1 the wol-k;, ve are goZug from tlae forty-fiXtll -tosva-rds the firf:

llatooll -;



MeaJkreenenf of a BaJ5e oX HorlnnoW-eathO 453 R:ation-; and ill havi1zgurecourGe to the getzeral talule of the bafes br altitude- temperature or correEtion ior eXpaIlfOll NVe arO

aScelldillg froln tlle bottoln towards the top: contrarily to the orXder in which tlle operatioll with the dea1 rods sras conduAed*

0t1 the.mortlingr of the I 8th of AtlguRX the Rantls with the various parts of the apparatus beiIlg placed in tlle manner juR llOW deScribedS the operatiotl F ras b.>gun by bringitlg the firR etld of the chaill- to coincide with the interSeEtion on the tripofd, anfwering-to the end of the r370th deal rod, and 4.3t feet dillant from the center of the pipek terminating tlle north-wek extremity of the 1DaSe The chain.beilag sIEretclled along its fivewcoffersby the- fourteen pQulldsrwei«t fOufpended over thex pulley at the firther eladS : and the telnperatures of the five ther- nometers beitag regifiered irl a book kept for that purpofe, a

iz8^e trace wasimade on a piece of card faRersed under the"^fea ther-edge at the farther handleS denotitlog the etad of the firRe hulldred feet. The chaill beirlg then moved on into the IleXt

five coffers, thofe th-at had been th-us vacated were carried for ward to prepa-reh for the tllird chain--lengthX and therel)y pertnit tlle firIl fet of lEands ito be elevatedL for the recept:iotl of the g;laEs rods; and fo irl fuccefl]lon Ftlth the others.

In this mallner we proceeded atld^^;in the courfe of the day vere ollly able to uleafure the lexbgth of ten chains<or looo feet, t?e;ig the fortyflxth and forty-fifth lzLypotllenuSes of the; lz* the firR of too ancl theF laIt of 6so fieetO Being arrived at thisxpolrlt it was ft3und that thefine litle otl the braSs Ilide5, tnarking the extremity of the tenth chain, fell {hort: of atao ther fiSue line otl the fame {licleg denotin:g theeellc} of the fifrieth glali rodg JuR tavoterlths of atl illch. Ifow it will appear hereafter, whetl ve coine to Dlew, by the experimellts with ttit pyromet;-erp what t11e real colltraAiolls=of^the chaiil and

,g15189



g4.D4 lWajoor-GeteralRos's Sccoan! +-t^B

glaSs rods vtrere, for the degrees of difEeretlce of temperature $

belosr that itl sshich vlaeir reEpeEtive lellgtlls we:re Iaid oR,- that . .

this f-lnall apparent differellce of --two-tenths of an inch l)e tvsreen the two modes of me?.furitlg the thoufarud fee-t, Ihould have lJeetl o.r7g3$ in. to have made the two refiults exadly agree, svhich is a real- dIfEerence of ollly o.ozo62 flsf an illC.

Suppofillg tilell every t:houfand fect of the bafe to have bee meafured by the chain with the fame attetltiot atld confe qelently with the farnes or rlearly the fame fucceIi (and therc fvlrely callllot be atly reaSon to doulzt o-f the pradicability) we Ihall have 27.4O4 x o.Ozo63 ii5 = 00365iII or a deSA of fomew thitlg more than half atl illc;h on the whole length of the baSe e

. . .

* WI1XI} the length of the chaln was laid of; t-he heat was 6642 a-nd that of the glaX rods 683. They will} therefore, only agree w;ith each other accllrately ia

theId refped1ve tennperatures. The -mean of tweMy thermomete-rs ir the fo r- chain lengths of the forty fi<xth hypothenuSe gave a-heat of 61°g6; a^d for the fix chain lengths of the fortyfifth the mean of thlrty the.lmometers gatve 59°*7Se trSe temperatllre of the 4oo Reet of glaS by the mean of forty thermometers vvas 659.3; and of theg Goo feet? by t-lze tnean of Exty tll-ermometers, it was bo°*S. Now, froJn theli data, and the expanElolls of Reel and glafsa as de£ero

olined hy the-pyrometer. the computation will Rand as foIlows o a 3[tle; It.:

5teez1 4°° 66.5-6I*6 4*9 xc>.03052=o t4955}=O45856 r cfnta2. l600 66.559 75_6 75x*oA578 = 3090I J l feet.

{4oo 68.o6s*3 =2.7 xoo2°68-o o5584}-o.27918r of I003

600 68*o-o.S _ 7¢2 xo.osloa_O*2z33+ l fecte

tI'he I0C0 feet of - eel hould have contraAed m e than } =0 I 7 938 the IQOQ feet of gla - ) " -- J J

iBut the diSerence was found to be @ ^ o2ooo£>

__

Thereire the erlor of the chain in (lefeA was -" o.-02ob2XP7¢404 ov565 in. or little more than half an inch on ttwe wholeiba-i

* :So



Bereazenx f or hfe oa Houenow*ESeath 455 9 ni-ce an agreemelt betweel) two refillts;s -with iwRraments

b very differellt, colald not iil to be confidered as aIto£l{hings and-as it rarely happenss thatSthe graduation of thermometers will fo nearly correfpoli-d with each otlzer as not to occafiotl a

much greater error, all wew very de{;rous that it could have I)een firther confirmed by--continuing the--operation in the rme way through a tnore corsilderable proportion of the whole lengthX But befides- the tedious nature of the doulzle meafurement, owillg to the lnultiplicity of RatldsS platforms cofliers, and other articles, that were now fuccelllvely to be moved forward and for which purpofe it had beetl found neZ ceXary to reixuforce vlue party of fioldiers with fix additional mell; tIle weration had already traitled out to a much more conSderalxIe Iellgth than had been expeEted; the iSummer was now far advanced, und the colltinuance of good weather un certaiIw; the coffers likewife for tlle chaillX havitlg tJeen Cotlo firuAed in a hurrys were s found to be defedive: in fihorts alt

theSe reaSons contrlbuted to itlduce us to give up for thv yore- fellt, ally farther experiment with the chairs alad to proceed with the glaIi rods alone in the completion of the meafuremetwr

Accordingly, oll ThurSday the I gth of AuguR the opera- tiOIl svith the glaSs rods was continued for the 15ve hypothe- uliesX from the fortyfourth to the irtieth inclutive. It will

be remembemd, that sn proceedirlg with the deal rods7 doulole pickets had been placed in ethe groullelS at the middle of 1;lze forty-Erft hypothenufeX or that point which termillated the xalsth rod reckorlillg from the foutll-eailt or the lsth frorn the north-weR end of the bafe. Now in returI<ing to this point with the glaIi rodsg the extretnity of tlle tssth fell Ihort o-£ the filk thread Ilretched from pickerf tQ picket jttR one-tenth of atl inch The expallfion of the brafs Ilandard fcaleS atld

Vot. IwXXV o o o t:hat



456 PFoF*^"eXlt Roots AcognE ff + that of glafs beitlg taken- itlto the >ccount it apwaPh ffiat fmall expanGotl * of the d&al rQdS Som the humidity of the

.

air mufi,, at this pOitlts have escealed: what it was eRimai at ln the general table by o*93t of atl inchs fquppiing na eror of any killd whatever to-haue arin {itl the exwutioW fLorn biringng the rods }£lt*0 cotltlj or othtwil:bv;

0:n Saturday the 2Xfl: o5 z4ugUEs the meafurement wag reS>unaed at the thirty-tlilwth Il:atiohX atld wnttlwd ir Sve hyp ttle:llliS tO the thirty Efth lxncluEiveX

-This day about nmt> HtS M.AJESTY &Ened to hotolar thu operatiotP ljy n+Is preferlce fort ttie bace of two. ho@s, erLterZ ing very.mtnutely itlto the mosle d cduding itX thich met with H:I$ gracious approbatiotl.

On 39tondely the 23C1j the menIBratlolli was ither confnutd for five hypothenuSes, tllat 1s, to the thirtll luclefive

()Il rutrda3 tht 24ths we proed with the meaXtemetlt for the fpaw of I4elietl hypothetluSess finiXng the buEilleii Qf

the day at the twenty*Iecond itatioa

. . . .

.f. . .. ln.s. r +O.383 Sor t eseefs of temrature of thk brafs feak from

^ * J55 deairokls) 62t to 63o -3soo fect X + oX65t proportilznable paxt of the eRimatvl ewanfilon from

t humidity QW . s _t

+ I Xo3+ eqv-atio-a of the deal rods on ,3IOC3 feetv

r +Zv3Ol br 6 excefs of the heat @of the brafs Xle fr

- 5S gla)irod54 t0 .36 obServed contraAioa of thc gla§s froathe lItb andu I s 2th colllztnns of the table

t +O. by whkh ti 5sth rod i11 fllert o£ the thzd.

+ I 96 ttlttl0n. Of thq g1afi rods on 3Xt St

. .. . o

o & I | biffierence of the two equationDsX unde>rated in tle >'93 t espnfion Qf thedeal rodsW

It



rege + v-Btfa on ElounIlow^Hea-th. 4y7- - It vvilI lle reInembered that: ill carryitgs otl thesoperatio-n

. . .

Wittl the deal rods double pickets were left in the ground; at the twetlty-fevellth-Ration, atlfweritlg to tlle extremity of the 8toth rod from the firR, or the s60th from the SaI} end of the lJafe. NowS otl arrival at this pointS tlle s60th glaSs rod 0s7el {hot the filk tllread, fl:retched from one ;picket to the otherS 24 5z5 inches. Here agaill ve fiXwd- that the lengtheIling @ of the deal rods frotn tlle moiIture of the atmofpllere differs -but little frolll what it has beeLl eRimated at by comparifon with- the Randard, beitlg overFrated ollly two-tetlths of an inch on the 560 rods. In this day's operation, in paivlng the bridge laad over the old riverS tEle meafure:mentg inIlead of being made in tlle hypothetlllfal, was carried oll in the level line, for the fpace of twenty rodsS Ilarnely, fifteen rods of the twenty- feventhS arld five of tlae twenty-Iixth hypothenuSe; wlaich occaSiorzs the alteration in the reduAioJl of thefe two fpaces, narked with aReriIks in the gelleral table.-

As fome trouble had beetl foulld to attetld the cro;lg of the grent toadS in the flrR mearurementX owing to the 1luln- ber of carriages that were corltinually paffilng-, the depth of

Tn. & 560 deal ( + In390 fOr It tXCCfS of heat of the brafs fcale from 62°

rods = q to 63°. : l AR00 ft. t + 5.258 eRimated expanfion Doln moRure3

,

+ 6.648 equation of the 560 deaI rods _, \ ,,

60 1af f + 8.3+3 for 60 excefs of heat of the brafs RaIe from 62° to 68°. 5d g s J + 1.8XI obServed expanElon of glafs l from colllmns sstka I S -E ] _ I.I9I obferved contraAiQn of ditto J and xatht lI2°° t t z.5Z5 over-lot the fllkthread

. S .

+ 6.448 equation of the 560 glaS rods _

(Differe-nce ovetrated in the EXpa-a51OIl Of tlle 5ft 0.200 1 deat rodse

O O O Z twl1e



4 58 Ma,y'QrGeneral bRos's Accxat of the the d'stches} and heigkt of the banks of the old Romatl way v.d*.

therefore treSels, fuiitedz for the purpolis had beetl now -prepared: and leA any accidellt might-- have happened in colldud:l:^

ing this part of the opetationX fo as *to oblige us to a repetition:,

double pickets lvere placed in the ufual manner itl the groutad twn rod lengths fiore the t-wenty-fxth Ration S to wllich we - cotlld have referred without gOillg back as far¢<as the tripod left at the tXentyXninth Ilatoll- tlle pOitlt from which we had<< departed irl tlle mornirlg.

Bad weather preventee3> any progrefs-beirlg made on tltie 2stli;

ands on the 26th- al1 tiaat could be done- vvas to meafufre tht twenty-fecond ai;ld twentyfirIt hypotheneSes-fi*

OI1 Friday the s7i, the workr wertt oru more expedi-tiouIly,

having LI1 the courEe of that dwy meafuted lix-eheypothe-niuisy

and placed the tripod atthe fourterlth at*rn.

On Saturday the 28thS eighe- hypothenuSes were meafurecls

uIad the tripod was placed at the fixth Ilatiorl. 21- this day'$

operation, being arr;ved-near the brsdge laid over WolSey Riverfi

double pickets svere pIaced in the grouryd in the pOillt anfw*

ing to the estretutry of the ttI7zd rod, reckonlng from the north-weRS or the sg8th rod from the fosh-eaR end of the bafe, that we might recur to them 1n caCe of accident; andE -the eighteen rod lengthss between this pOiIlt atld the f}xth Ilations were meaIStIred on the level, illilead of the hypotheZ xlufal line7 which required the alteration of the reduEtion as diRinguithed by the afleriik in the Ileral tabIe.

01w Monday the 30th of AuguRX the meafurement with the glaSs rods was completed * ; when the extremity of the s37cth

rod s The gentlemen who were preSent aty and affiRing iny the Ia: day operatioa

ert Capta;n :Bas5BvX MrQ C;Rw1LE} Ssr WXtssx EIAN1LTN} gr teas;ns

d



Meafarement oJr a BaJR on Hounnow-Heath. 459 rod over-{hot the center of the pipe terminating th;e taX towards the fouth-eaR by I 7.8 7 5 inchesS or I .49 foot Hencea vhen the feveral equations for expan^fion3 are refpRively taken suto the account, we Stld, that the altBratiotl of the deal rod-s from the humidity of the air, whic3S,- by mmparifon withXthe RandardX was apparently m-oR confiirable iw the firlt atad fecond fe&tions of- the bafeX has now wholly- vaniShed, that t$ to f<,. the total amount- of i-St has lueen over;rated by zo*964> inches$; andthis.isthe contraddorwvcirculnIlalzze-that has

been formerly alluded to; I- have already fuggeZd what app@$r to mb to kave bee-ru

the ollly three poffilble cauSes of this difEerenGe7 founel between the ellimated aladi real expanfion of the dal rads; aIld 5 we are to abandon that r3zeafurment entirelys it is->of lsttle or no importance now toS aldeav-our to dificcery were it poffilble rhellce it may zhaw aren. If azay errorX was adu;ally; corx=

and Dr. Us HER, ProfeSor of hAronomy in>>- thev College. 0f>! Dublin. This 1ak gentleman was fo obliging as to obServe, with the moR fcrupulolls attentiovj, throtlghout the whole operation wtth the glafs rods, that the coincidellce of the fecond with the fitft relnained un-dOurbedX whllB that-of t^li{e thll-d tith the fecond was completing,

In-,

131° deal| + 3b389 for x° of the;brafsfcalefron3 62° to 639*. 97+<><;> ft j + 24 2 23 eRimateRexpanfioEl from humidity

_ . .

tM7.6 I 2 equation -of the- X 37o deaI to&.- . .. v s

r + oo 336 for 6° of the braSs feale^Erom 62° to 68°. 370 glJ +- 5.gsg obfervecl espanfion -of-gIafs, lfro}n colllmns Ilth rod-s = ] -. .8O2<o$airved contraAion- of dltto J and sxth. . 2y400 ft. t-I 7.875 fpace by which th 1 370th rod over-{hot the pipte.

t .e s . x .

+ 6.6+8 eqluation Of t} ] 37o glaEs rodsQ

:o,96+ ov¢r-rated sn the total cxpanfion of: the deal rod. X - luitted



+6D or^Generuzl R^ovds ACCQ2X-! -+ ttxe-- m1tted9 svhtch is the leaLl of a11 pr-oljable it could ouly have happerled at tI-le place of the triped by larirlgilag a wtro;ng point of the iNtetn over it rwllen the operat;XJIl was refumed But it is we]l Iitle3svaS laow mucll care at9ld paills were takell to prcvellt ally thitzg of tizat fort. Itldeed -the hypotlletlufal dif- tances9 as given by tIae £haz agreed {o nearly among them felvesS tllat evez a iot or tetl suclles would have made fo re nlarkable a diSerellce 1tl tE1e f1tuation of the tlext picket S$

could 110t have pafled utlobServe(l BefdesS in returning vitl the glafs rocls, aRer paXlug tlw Staine$ RoadX the 1neaftlre- meI1t was gradually folllld (-without AJ}y leap svhatevel*) to over-Ihoot the picketsS arLd at lal} overreached the fouth-eai:} pipe by r7*87S stlches I am therefore illclined to believe,> tllat the diierelace ariSes partly fi4otn what nzay have l)eell loI} by conflca:tltly butting one rod agaitlR the otherS whereby the e1ld of the 137sth did IlOt reach X near to the llorthoweR pipe as il: ougXlt t-O) and would have dol1eX if the rods had beer applied to each other by coincidet1t litwes It muRg however lse confeffed that the near agreement betweetl the glaSs atld deal rods Itl £he uppe-r part of tlle heatll feems tlot perfeAly recotlcileable t-e this fuppotitior. 5evertllelefsX the. defcent beitlg quickefc and the irregularities of the furfice much more collficlerable 1I1 the lower than tlle upper partS might produce folne eieA in oIle which did IlOt take place in the other 13ut the chief part of the di«erence I take to have prc)- sceeded frotn over-rated expatlfion; that is to fayS the rodsg whes1 hrought into uSeS cotltra&ed fooner tban we imagitwedS and thereby gave a thorter meafure r:han what was ailgnable {to tl<¢m from the rlleall of any two or more compatifotls.

T. ]e



MeHzrblment of a B4fie an MounfIow-Heath. 4ht-; T!le laft day of Augu{} was etnploved itl cliichargillg th-e

pal^ty, aIld removing the various parts-of the apparatus to Spr;Jg-Grove ''HouSe.

DeMcraf tion of the ldicrs/copic Byrozneser, made ?JH of fior dvZer- n;nxng by encteriment the exltJ on of thPmetals concerned - Zh-e meaprement of the B+. 'rab. XX.

H-ar7ingS in tIleS preceding part of rl-]is PaperS give-n; a very mi- rlute -account of the aAual- operaMrbs in the fieldX -that tile- PublicS lJeitlg thus itlfbrlmed of-every citcumRanceX might be the bettei- etlabled to judge of the accutacy of the refult, it retmaitls yet to ptoint OUt:7 itl what manner the equntions for the expanSiotls of the llandard Wcale) fleel chain and glafs rodsy applied- to tlle apparent meafitremen-t of the l)aSe, in Ieveral of tlle preceding notes, llave beerl obtai:tled by means of experiments with the pylometer

It is fuflicieiltly well knowla, that matly years ago a very iIlgeIlious and valvlab:le Member of this Society clid pulolilh in

. . .

the PhiloSophical TrataC<tions (vol. SLV1:II. zE75+, N° 9.) an a-ccou-nt of expetiiments <iade wi-tll a pyrometer of his iW- retation-. No doubt was enitertailled4- of the accura£y of the experimctats llere alluded to; on the contrary, they will lDe confirtlaed by the account nos^t to be given of there recetatly made, with which they very tlearly agree. 13ut as diSerent pieces of metal of the fatne kind Sare certaitlly -fuSc-eptible of different degrees of expanfion, it vas judged bet} on the-pre fellt occafong to pu-t tods to the teI} of thoWe very met-als that had been lnade uSe of irl the aAual meafurerzzdlt of tlze baSe+

7 FOEj



46z llAajor-CIeneul ]t0Yt$ Sccoant of the For fuppofing both rSets of experiments to twave beent made wtlth irlrutnents equally perSed, and to have b-eetz iIl other refpeAs etually well condu8:ed, this muIt always b-e coIrfider-ed as tIle lmoIt urlexceptionable method Befdes9 the-expanfion of rods -of the length of five feet bng aScertained-, the utlavoidable crror of obServatiots of this deli-cate lflatu-re, leconles leINened itl proportion tosthe excefs O4f their -length above ffiorter rods. In thefe new^esperimetats too, arlother fort of pyrometer, in- retlted by Mr RADISDEN, has been applied-, of fuch accurato conIEruEcion that it feems not eafy to improve it.

The mocroCcopic pyromete-r, f-o named becauSfeX by means of tsro microfcopes attached to i-tS the expanfiorl is lneafured, confiRs of a Rrozg; deal -fralne five feet ill lengtl<, nearly twenty-eight inches broad, and about forty-two itlches irl height. The elevatiorl of the eyeZpiece fide, or that which prefellts itfe;lf to the obServer, and alfo of the micrometer end, or that wllicll is tonvards his rigElt-hand- as well as the general plall of -the tOp5 are reprefellted by a fcale of one illch to a foot, or one-tweffth part of the real dimetlfiolzs, ill tab. XX3

whewre likewife may be feen the angular view of the fiXed end, together witll plans fedioIls and elevationsX of fevelal of the pritlcipal parts, dotle to larger fcalet. From thefe, it is hoped5 the corsRrud:tiotl of the machine will be eafily vlnderItood, wit}lout etlterillg into a minute defcription of the almoIt 1lum berlefs .Emaller parts whercof it is compofed.

0tl the top of the Eralue, two-deal troughs, upwards of five icet ill leng;tll, are firlnly fcsreured. That towards tlle obServer overhazlgs -the frame fometlling more thall an itlch: that on the farther flde is even with the leack part. Each of thefe tyrouglls, which are alJout three itlches fquare ill the infide,

w(oiltAillS a caR-iroll Satldard prifin, svhofe fidex ale I j iIlCh

The



MXretnent; of a Bayte on He;unflow-Eleathe 463

Tlise malluer in which the prirms ase fiIlened to the bottoms of *tIzeir reIpeAive -t;rouZhs, -alld the nsature of the apparatuSes tile3rF

carry on Rtheir extremitieA wiI1 be readily concveivedX by refirZ ritlg to sthe particula.r ,plans - and.elevations of them, compre- heti1ded in the grou,}? of eight fmall figures towards the right laand of the general -plalw. Four of Xthefe appertain to the left hand or f xed m.icrofcope; a;1d the other. four to the right-hand or micrometer microScope, fo diRinguifhed becauSe it hasf a .micrometer attached+to' it. t ]3y means o f the larafs collars svhich embrace the prifms, their left-hand or ;fixed ends are Icrewed-dowll extremely fali to the brafs pieces whereon they eR, fo as to-be--perfe&ly immoveable-there with regard to

their troughs; whereas their right-hand ends are kept eafy, yet without thakej ill their collars, that they-may contraft or slengthell freely as the temperature may requtire, svithout occa frolaillg ally RraiIl upon the parts. tlAle priEm :in the neareR trough tnay be called the eye-piece prifmS becauSe it carries the eye-pieces of the microCcopes; atld-that in the firther troughs, the tnark prifsu l>ecauSe it carries the marks or crofs svires at

which tlle microCcopes refpeAively poitat. The troughs are covered with pitch in tl-le iI-af-1de, totntake-thernholdwater; alld each has a cock itl the lefi-haIld end for diScharging it.

iBetsveetl the two deal troughs, one of copper, as a bsilers is placed, fomewhat Ihorter than the fo-rmer, but Rill upwards of five feet in letlgthv Ist is al)out 2 in-ches :broad, and32 i} dejpth. The center of theX boiler, or rather the cellter of the ol)jeEt Iens svhich Rallds in it, as we ffiall have occafoIl Coon to pOillt out, is diRant frotn the crofs wires of tlle mark 5.8 v slaches, at1d from the wires of the micrometer attached to rl1e correfpolailitag eye-piece zo.33 inclles. T;lle boiler reRs on five -fnall rollelZs, ot1e beilJg fixed to each end of :the fraxne7 andR

ATOL. LXXVo P p p tll:



^ j (>$att'oY9.&;88eJ&f t

e tiet threef th th-e wrates-*whiCh run f acrofs it . \- Thts; >o

. .

per- trough hu liElQw-iSf ai: coclt inwthe? left-hand end-; and irt the gelleral -plan a c-a-fl s irotl prifin is ;rtiprefented in t ; ̂ but this laR carries notapparatusS as- thc)IS i-1) the wooden troughs dof beiilgq exa&ly of the lengi of I6ve - f@elY; alld oMy placed there as olle of the rods w:hafe expanfiotl >-was- tred, and-:- to lkeur-that- ffie machine W28 capable o£-rewiv^stlg a; ro-& o£ t-ht;1veigh-t and rnagilitudx 0 -0 ^ - | ^

By-referrillg to-Sthe gelw-erul plan- i^t wilR be iMen, that twelv hanaps are madeMuvSe o-S:tovbrlng0th@ water ixnw thx c^opper taboilv They hld;on fottr Ihelves, three- :n each wlrt:maw-£- br& by the crofsS braces of- the Same. They can readily beX puShect Evirwards or drawn bacld-wardsy atld whenibaAually;-i-n uSe, theirs laandles are olwly feens pre3eEtitig im unir ti wpser. I15 was found, by bu!rnir;g oil in- the lamps7 the heat of the water. ecyuld llot- be raiid above zogO ior 210° >.9 bu>$} svsh fpi-rits o£f evine it was brought into violent ebu-llition. 57he p:la-n- of the frametlikewife Ihews, that-the tul3e$ of tile microIdepes are- fidb-divided i-ntos IWYeral difiitlA partsSg and :that otwe of the£i

-

?arts is attached<-by a collar to a mahogally pnfm; fw^hic;hz --reachest- . .

firom olae e>tld to. tlle o-ther. But the ufe of thefe ontrivances st will be beft to defer Ii3eaking- ofs till after;-- h-avinSg- defcr-ibedL: the apparatufies lthat are pla-ced withitl the copper bailer.

ht the bot-tom of the plate the lSoikrt is teprefetwtedgAboth sa plan and laillgituditlal feAiol}s- > a; kafle of on>sourth part of- its real dimellflons It contains witlain it t brafs fiides t-lle one lonzg and the other IBort; whlch, £rotn thre braces tlaat- bind the cheeks together, ver.y ln;u-ch refemblbv the foHrm of a:; ladder. The lorlg DsideS whoI"e cheeks- are- tw- sin.ch cleep,; reaches altnoR tlle whole lengt-h of the copper, althouglx etery wilere - ullconneEted with it except at the po.ints 4 and R - At

X > - a tiwc



hRedJ:44resf eZ f a e on i-<)u]*Dow;fteath 6! . .

<the firf} of¢thefe, two Ilrotzg pietes of l)ra-fs, fixed to-Ehe cheekss and notched u-nderne:th, embraice -*the ends of a brafs cylin

.

drical ltar fiPret-led -to the bottem. At the laR, the -cheeks o-t . . .

the Il-ide reLt- on a roller. Whellee it follows, that the copper and tEIide remain-immoveable with regad to cach other a-t A; but from- tllence, towards either endX they have full liberty to challge place; that is to fay, iO expand by heat, or co:ntra&- by cold, in: allyb proportioll their diSeren-t natures- may reguiree The left-hand end of th-e {lide is fh-ut? up by a Rrong perpeIl-" vdicuIar piece of braSs, cozueEted with the two fide nugs which fupport the olzjeR lens of the fixed mierbfcope, whoSe cente:r correfponds accurately with zts iIlWa-rd face. Thss piece being frmly fcrewed to the cheeles of the -Alide, and couriter-;arched toutwardly, forms a Erong bute fQr the- fised etld of the ex- Xpandillg rod (fuppofeed -here to ibe -the Reel l)ar) to aEt agaitl

Within the right-halid etld of the- lellg nide -refls a -{hort one of about I4 ;1lches -ir leIlgth, whofe cheeks are I 4 inch deep. Its out-srard endX at C, reRsfon the cylindRrical --fiurface of the laIt brace of the lot1g Xlide, fitted purpoily to vreceive ;t'9 svhile a

;t]arrow loJlgituditlatl bar fixed iIl -its inward elldS at DE in the feEtioll, xnoves freely i1w t-he laotch of a bridge , framed for it in the long--llide. Tne -outsvard:-elld of thxs fhort nide is fl:wut up i-tl a-fim;ilar marul1-er witll the loppefite end of the long one

This end-piece is atfo conneEted with the twofide rillgs which-fupport the tube COll"tAilliIlg the oMed lens of the nsi clometer rwiciaCcope, ^ihefe ceIater is perpet1dicularly over its inward face7 and being fortitSed 1outsrard1y lvy an -edge barS it tioilNs a butt for -tlae expandin;g end of tlle iod th;lt is itl -experiment to puffi agairlIt. B-y attezwdil1g to the plate it wili be perceived, that to tllis endA of the boiler a braSs tul)e (R) is Exed, svhich corltaills withun-* it a braps red,> furroundecl by a

}) p p X helical



466 or0General; R@3 3rcount-¢ f t helicat-ReeI fprillg:-; which aEing uwn a-0broad ffiouldzerrF ffie md: prepared. }for the pu<pofie, 0 thereby SpreXesits lillwardt end} which etlterss the beilerj agai lk the perpendicul-at fuice of

the endopiece of the ihort fitle^< ;1 fThus<> thfgtlleriend of the

mdv in experimetlt, :fuppEd now to lje itl its colltradted Itatey is conantly-:made to bcar WagaillR theC hlrfuce fthat is utldero the

:fixed mi:crofcope. But the-applicatioxl- o£\heat7 the irre

fillible fiorce.-of expanfierl irt tte-.rodtobliges-btthe. fpr.ing to gi-vt

way ;+ tlle ffiort ni¢ chat-age-s it-s;-placX atld withs it the objeA lerss of the micrometrJ microfcope moves orr a.e propor- tionable t-o- the degree of heat thatw is applw&- atld.itXis this diRanc-ey meafured -bJr 0 -mearl5w of S the micromerer, as- hereafter will- be {hewn, that deernes the quarwatitf of rexpantioll;7>orX t}}e fpace by Wllich tther rod -has letlgtherled FCrom w the u platt

- A will be further-*;obServedt that the rodtin experiment reRs onr- the fxlrfices of three--rollersy about atl inach in diameter; aniIv by means -of three pair of milledSneaded nutS I i inch in dia- -meter whicll lnove- oll axes>th2;t arWe for^med into irewse untiLM they almo touch the fides of the rod,i thLis is hept -in its trua celltrical pofition7 whatver may- lbt its fUrla or latcraLg dimenfions. - The microCcope-towads theFleft*han has beetl denonllnated- Exed, becauSe it correlWolads wLth the firR or fixedR elld of the rod iru experiment, and- llever- shallges its fplace while theSe are-- of the length; of fite feet But -it aWearitlg to be of coI<fe- quences tllat the expatlrlon of the - Ratldard braSs* Scale., which is not quito forty-three tushes long, Ihould be determiiled, thq pyrometer ha;s therefore b-een adaJpred¢.for the reception of ally rods lefs thAn five fEetg.whereby it is made-more univerfallyuSefulQ For this purpofe it becotnes neceSary to move the marks alld eyetpieces of the fi}ed microScopea along the;r rebedive prifimsj,

- to



SIevArefflen! of a B;J*e oa HouIaflow-Heath. 46; tD the proper -pofitlon for the rod that is to l)e tried. Neverthel:eSs tlle ol)jeEt lells remains irl its Woriginal place; and iIlXitS Read awotlaer lellsf of the fame focalf diRance, i-s fixed oll a fimilar etldpieceX that can be firtnly clamped to- al]y correEpolldillg zBlace whatewer of t-*he cheeks of the long fide* - Hence will appear th reafotl for I)realritlg the Screelairlg tubes of the ml crof£opes vinto -fe0reral parts, and the ufe of the maliogatly prirm> $10ng: which the thick part of the tibe moves from one end vto the other.

The; pyrometerX IiFnce it was firR made -and ttled, las unde gotle feveral fmall altelationss by way of improvemellts,>whicll it i,s. now urlneceiaryY toS defsfibei prticularly C31ao- of thefs 6 was the applicatiotl Qf crofs Ievels to the psarts ot the tulJe (SS V .. 111 the general pIan) coxl*le&ed with the obJeEt glalies. trho- manner in which they are fixulo OI1 Will appear from the rem p>reSentations of tllem iD the lowermofl: left-handr. angle :t11e plateG Ailld the fedcion at the rl«t-halld angIe IBews the ap- pearance of the double l)rafs hook>, utliverEal joirltg alld milledt headed IlUts applied acrofs; the- tniddIe of-5the boiler- (at TU)- svhereby t1> level5 are.btou;ht to beconfRetlt>wllcn-tile.rater is boiling; with the pofitiotl they had beetw<aguRedvto whe1s the temperature- was at fireezingv, t3zat is to ftayX tlley are kept parallel tothemfelves;iz l)oth Rates. ;This:was thoughtneceCB Iarys I)ecau^Se the applicatlotl of the bZoilillg water ftink the xniddle of the ifllde a fmall matter7 and thertby tnade t-lle levels Run outsrards.^

Tlae microlaleter fo often mentiotled, belng a very- elEatial pal^t of the machineS is reprefeDted lJcath itl elevatiols al.d hori- zolatal feAciow to th-e ft111 :fi22. Its claief parts COtl of a mi-¢ crotneter Reel fcre0w, which worLs irl tl-le fquare IlUit O5. a brafs flidKe>> uhilc the piaxwe part of it enters into aslougi brafs.>focfkerX

xlicely



68 >;or-Ge?esl-RoYbs SccounX f ttS>c nicely ground tto- receive- lt, and thereMripreventtllg dlfilbAe

. . . .

-To;:thekuarerlut, otleend:-o-fawstch-thaia>¢isattached;-the ot-lleir elid laaving -paICed aroundcis fisedtto aVbaral, which- COIl

x +

tains a watch fpring :-Ceiled ;up -in t-the uruaL manner. By this- <colltrivarlcev any liMs of time irL the :motion - bf the moveable <>wire, fixed to the fquare fide, iws-:eie&ttally prevelltedX whe- <ther>the fcrew tbe ttlrtled baAwards or forwards. The fixed -wire3 fo caMed becatife;it is-only made;tlfe -of occaElonally, ap- gear;s itlkthe ele-vatiotl t-o the ileft-hand of ethe former, atld is -b>farther remoGredi iom ithe oSf-eserX beirlg attacMhed to;the ovaI sfide ssrhi£h bounds the field of the-mic-roineter. Sllfis wire ;s moved by the irffiertion of a rrlilled-headedl key (altlloughinot tepreSented itl -t}leiplate) fittea to flxp upon the -f4uare end Xof ts proper Screw, which may b-e wfeen, in the elevation, proge&ng alove tTle mcrometer head It Xhas bs little mototl, being 6nly irltended0-for the meafurem-etlt --of IVall diflierences of;-ex- Tpanfqll -ore atly fmal-l fpace, by leaving -it thereS {Hi1le- the other xvire is repeatedly brought -to -coitltide svibll, :and agaitt

dopart -from ilt. For particular-purpofes t-hts ;wire may be uSe ful ; - nevertheleli, athe infirumett worl1d1 ha-ve Lperformed rery

. . .

vell-uithout itDo :^ . . . .

Tlie conltruAion of the Xmt;rtScopes wiIt lte readilyuunU

-derRood, ly referrirlg ;to -the figures under that laead on vsthe righhanal flde of -the Mplate) ere tfle relatisre fitua ;tiOIl-S of the differetl-t geglafles, w-ith reDggd to ths wires or pl;ace of the rnagL;<ified ilmagev as weIl as X the eye, are truly relXreSezated ill tlleir real dimetlfiotls; but-tlle dRa-llces hom ;thefe to tlle -oljjeA lenfes and marks refped;;vely, are conZ .9t\ra.aCdior -btfokell -oi9 fr0tll Wanit 05 fu,ffic'ltnt -r00m to deli\2tate

them otllerwlfe To illcreafe the azzgle wOf vifion in microCcopesKs

tt kis always rlecelSilrg that they iho-ulds have-at leaR tssro eye ;la-I3es, alld the 15Xcd lxl-lc-roIcop-e -in the plat-e illews them irl

- tlleir



aregen! o,fS a B#e on EfiounllowHeatfi. 449. eir uI;al xpofi-t-ion? the tmage fFom the obieA lens-there being: iraled between the:two that the dilperElon ofl rays in>the Er may beScorreAed by that of the fecotd. E3iat although this COt1-

RruAion ferves periEly wel-ltevery prl?ofe oAf the fixed microZ kcwpe, yet it could xor;anfwerin the tnov-eable ones tohich the: mic*ometer isal:tachedy wll;ere equ-al partst-an i:lnage, C their rnotion, a-re to be meafured b;y:the equtab!l-e motiono of the ob- p& lensS as {hewrtS lxy- theM micrbm-eter. for lathat cai, the itterpo6tiotl of aul- eyeglaIb-+ before the ituage was brmeds would not: ollly have diminiied- its>>flzeS alld thereby relldered t3he meafure- lefs*accurate>; but llliewi-fie>+by refraAing-tlle oblique p¢nci-lss tnore-- thian thoX ller t-he ce3Merj it: wonIdL-

. . .

lhave de-Itroyed tIe equality of the- ficale atld mad@ qual -parts sof the olJjeE it-felf to llave bee>reprefetlted unegallyF ill the magnified-imagev; aM0-:corlfeently erron-eouily meafuired by- -unequal: parts N of thee niclotnMeter; It was to remedy a defeA of this forts t-hat l!dEr. RtMsDE propeferd- his tw tRem ofz sye-glaXess deferibed: irle the Philo-Soph;Cal- TranfaEttons} vole

EXXIII. </ , -:N° Sor Aild he has he-re appliedb tilatX $7Ilem lIl tt conflru&;o-n of tlut micromear m-i£rof¢4pe S where it will les perceiv-ed,; that; bothh- glais vIlatud between the- eye aIad- tEle image,- svh-etrebyi the gresat=-maggitude of thuis la-ft is ob- toufrly prefe-r-vedS as welE a--s<the j;uPc Iimilarxly of all its parts to thefe of the ohjeEt itfelD- :

Witll reg;ard-to the Scale of the rrometerX st i5tt iN tlle firR place, ! to be ob-ferrd7 that->the head of the micrometer fcrewy urhich is-line.*tetlt-hs of an inch- ita diameter9 is-divided into Efty- equal>+ palts>> cacll -of whicht -beitlg rWeckoneclvtwoj it is

Serefore lu1nSereds to- xes-. lESit-five loev-olutions of tla- headXf beillg equal to¢O.+y717S -of atl xtlch>- as meatilred with ;reat- a<uracJr by-Mn Rs;DENss^- f;raight-line engirse,,^. w-

.followsf



47o MajorgG@texl7gRoY9s Accoun- f tbe . .

fiollowss thatrthere-are 79t .27 ireads09of the -fctew in- anx >tncll@-,, that feverl revoltltiorls and nearly 'th Xparts move the wire;of the lmicro1:Cr one-tenth of an inch; -a£ud; that Tth part of -a res-olutiolS or half a diviE1otlS anfure-rs ^to a motiotl of f.omez thtag more thall o.Oool*<of an owch

vHaving thus-obtained the l¢u-mber Rof olutioils-^arld pares d

the micwotneter (7.t 3) correfpatlding t0- olle-terlth of an inch at the wires, it is fufficiently-obviousS that tshe number ianfweriIlg; to one-stenth LM at iuthe mark beilg likewife obtained alld aLdded to the fortre-r, Rtheir fam tvilll give th.e meafure of orleZ renthAat the objeEt 1ex1sS or -the fpace by svhich the expanding

-rod'lla-s'slengtherledS as -ih-ewn by thetmotlon of the letls -from

o to t This meaire of one-tenth of atl Linch at the mark oras aScertaitled XX1 two different ways anld the -;-refults exadtlJr agree-d wtth seanth other. i:h1 rthe f rLE / placeg a ve-ry-: thin ivory nide, hereon feveral tzwetltieths of an irlch wer-e nicely dividecl by exceeditg fine Rines, w.as prepared, arud made to move ill -the markls;v-llere the braEsiflide IlOw exiRs.: A-candle being then placed behilld-itat night, while the pyrometer Pcood:svithin doors and the miclornerer wire beitag repea-tedly movedXby tI}e Scresar, zitS COillCideXlCe Wittl the lines s difiinAly feen througl theivo-ry; whereby -two of the fpates were found-to le--meaZ fured by 2+.>g3-revolutions osf the head. Tlle fecond nethod was, by meatls of tsro exceeding fitle Uwires placed parallel to each other QIl tT:l-e bl*afs flde <ewe tthey now remau at the dsRance of one-twentieth of an inch ;on -eacla f1de of the- itlterv

IeEl:ioil wires {a5 may be feen by obServillg the real lmark, or

rsther lts tnagn;fied image, as Ihewn ill the o57-al field of the micrometer, ill tlleQcelltral figure of conRruAion >hesrevoX lutions of the micronerer aRfweriag to tlle diRace betwec theSe parallel w-ires svas, as t3efore, foutld -to be z4.g3;.wlwich

leil;



3MffieXfXtrmgnt of zz Be oB HomowRosv*1heat1^l 4yx txing added to -7. I3- Wt t-wave 3%od for tile tlutnber of revoluw ;OI1S meAfTlri11g a SOtiOI1 of one-tetdl at the objweEt leas9 0lV tthe expatlEloll of -oiletentE10 Itl ttlis matlt;wer Mr7 RANXSDEN OI)^ tains the fcale of his pyro£n-ec-r ilzL -the eafie-R at-d tnoR <fituple way imagitlable7 without atly -necefity fbr knowing the abSew lute diLlatlces of tile cbjeA lells frorn vlle wires of ttle marli o -o11e :hand, aIld <thofe of t^Swe microlucter o1l tlle other; diRance$ -not eaIily aScertaitled by aAuiL neaf^uremeIlt* ^oll account of the polatioll of that glaSs itl its cell, whicih carlllot corovexliently Sbe corne at. Thus in tab. XS as well as -ill the aullexed

figureS l>M being the objeA at:the difl2nce of

th-e marli7 equal tto - -one-tenth of an: inch; iLrlM

<thell mlvvill lDe :its rnagn;Eecl ilunge, in xprew d POftiOI1 tO tl-le fortner as sz o ts to o M. And, > -1 If tlarough the poillt pX -the place to svhich ° jSi the objedw lens o Ioas beexl carried lBy the mow tiOI) of the expanding rod,;a lille Mq be drawn parallel to Llv we lthall haare W12+.g3+1q 1 7.I3-mq=32.o6 the rlumbei /of revolutions | of tlle micrometer meafurillg op the expanfion -- Halrillg tllus obtailled t90ze total ntlmber of

revolutioll$ correfpondillg to sq; alad hasiing i like-wi:fe meafured the total diIlance mbI- \-1

26.I44 inches, a fpace eafily aCcertaiIIed le- \g\q

3tweell the wires o£ the- microlueter arld ;thofe

-of the markX the partial diftances ma aIld oM njay tlle-ls

-be readily fotlIld by computation: for; szaq : Gl e' gM ¢-^no o*33 illches; atad mq; mM :: op -* oM-548X4 itlctles

Ill order to filaith tlle defctiptioll of the pyO4omerer, it ^s

tolaly 1leceIRry- to obServe iErther9 that the circular fcale:,

feexl ill tlle elevatloll of rlle rnicrolnetern wha oWe sero apw

YOL. LXS-v. Q q q pears



+72 Major-Greral;Ft^ots Atc!anz of thic pears b colllclde with the- dart o11 tlic plane part of the braI} is tlaat hich Servea- hy its motiotl to reg;Rer the turlls o:E thie head. A forked 3keyf fitted to ellter the holes near the CilCUS-

ieretlceSof the cilcle, is tmade u-fie of ir the aAjuRrllent of this zero. 1^he circle nzould tzevet be tti-rned back>Tards or tosvards the left lell t-}e- sratcll ch+al DiouLd thereby be: throrra off the Ibarrel but always folowards- or tosrards the rlQgh-t even if-it Should be 1leceffary to move it almoR all etlti3re levolution The ;erQ of the head is that s^7hich ffiould be firfi ibrougiwt to-cor refpolld ssrith its; proper clartO They may be feen to cDoillcide irl the Ilorizotltal SeEtioll of the rnicroleeter, and the dtparture of zerogfroill this dartj illdicates, by the number of divifoils that are interceEtted, the ualue of anX fradiollal part. of R

3CVQlUtiOll os

;ONS-/ 6f zhe gerenfs with- tbe tromerezeQ

Although the itlRrumellt which It have hRere erldeavoured - tc; defcribe was begun tarly in the-wiiit-er of I 78-4 yet it was rlot finilhed- till the begirlllilag of latApril; at wllich time itX sras bro-tlght to Argyll-StrectS and: being pliced: trtlly lSeveLC on the llolie patement of the yard, was covered wtith an oil-cloth caIlopy that the experimcnts might not be interrupted by

w . )e

raloy weat zer. -

To fill the three; troughs completely- it requIredt from twenty f te to thirty pouIld-s of po-atlded iceX which was always- put itl with great care, fo as to apply as compaFtly as poilble to the RaIl- dard prifins alld rod refpeEtiveltyX with but little common svater X

* When cotnxnon.xvater was vlfed, alttsough not-- in any very collfiderable pro portionS the thermometer ltepg always half7 -and>imetimes three quarters offa

$-t¢t ive 3vz



DIeaJaremgnA of a }e on Hou1wllow-Eleath, +y3 at firR added; it havitlg l)eetl found itl theIE esperilnentsS tllat ice water ollly, fuch as dlaills fr-ona the ice ItSelf, is that which Ihotlld properly be macle ufe of to lnix wvith the poun(led ice, itl order to brzing the whole maSs to tlle true freezing temperature. Being at the comrnencement utlcertain what time might be neceIlary for the rods, eEpecially wh.en of fo large a fize a$

the handard prifmsX ltO acquire the juR tetuperature of freezing11, at firR the ice was put iilto the troughs over n1ght, to prepare for the coIltinuation of the experime1lt next morllitlg. But after many repeated trials, this precautwon was found to be aeedlefs; a quarter of an hour being more rthatl ftlfficient to give to a11 the freezillg tetnperature as well as to render the lens on tlas expandilag rod Rationary9 after the urater fupplying tlle place of the ice had been brought fairly to boil.

The ilaRrumellt, in its firR RateX havitlg ill fome cafes made tlle expanElon aear to be-progreE1ve, alld not equabl-e; therefore its rate was attempted to be aCcertained by llotlug the prot greSoon anfsveritzgto 60° 120ox alld 8oO abovefreezillg. But wllen the illIlrunleIlt was rendered perfedcX alld that tlo Senfible difEerence was fiound between the exwpanfion at the lower alld; that at the upper part of the fcale, a fair mean beitlg talien be- tzveeil its aScendiIg and defcelldilag; rates atld allowiilg for the: diiculty of keepitlg the srater for awy length of tinae, pre- cifely to tlae faxne iiatertnediate heat; tlletl tlais tediotls myode of candudirag the expetinelats sras given up, alld the expan-fioru

^ I So° srras at once det:ermiLled by bringing the svater to boil aroulld tl-ant rodX svhich but a little lJefore had been lyi-ngfirl naelting ice) and which the Randard priEms fiill -COIltillUH to

610 throughou£ each e;xperimeiltS care lJeitlg taken to haAve a fupply of pouulded ice always ready to keep: thefeitwo tl*otlghs zauite full.

C! q q 2 ' Two



47+ varCe-rer,21 R:oY§§ AcoUf! --of tSe Two obfervers are lleceflary fSt the t«eEi:Etal-;application o£the

pyrormere-r. Ple ho obIerves witll the fixed microCcope, takes care tllat its oEjeS Iells is kept in its true ple9. that is-to day tllal: the wire itl the eye-piece accllrately biteScs the i;>nterSeAionl- vires o:f tiae mallK. Tllis he is ena ;5led to do lby--meaIas of the apparatus: attached to-the fixecl cad of the b(Jileer as willibe beR conceived l)y obIcrv-itag the plan (<at W) alollg with the ele- vatioll of that elld placed llear it. The apparatus confiAsq o£- two milled-hea-ded fcresvsX sve:tkillg in lJrafs plates faRetled to the etld of the frtn-e, and-aEillg--ngazoa a fm-all cock which projeAs from the Iovrer part of t\lie lSiltr9 wh@l-eby this laR -/receives fuch lollgittuditlal moti;on to ard fro on its rollers, asE is fuicietlt ifor the adiuAmellt of the lells. - EIe who obfierves with the microinerer microfGope> lwavillg lirought the zero ofT themicrotnete-r head to its dartX as fhes^7la ill the he-rizontal feEtion, alld alfo^- the revolut-ion zero tos its- dart> as reprefented; ils tli.e elevatiotlS takes careX whell the roQl has acquired the; freezing temperat-ure7- that the tnic-rometer wire bit-ed:ts tlle in- terfeEt;oli wires of its proper :1narlt.v lnhis :he :efi&s by work ing with th-e milled-heaeled ficre-wS -reprefeizte-d ixz theSplan atld

elestation of that tnarkS wherXeby the mark itSelf: is rnoved uIltil tlze btSedciool ts accurate ;> and duri die wwlacle of th; time, t1-1e firR o6Server tnuR be extremeRy attentive to heep hiv lens adj-uRed.

Orle alElllal<-t at IeaR is neceff^at9 -wllofta^kes hisZilatioIlo the oppdite -fide of the pyrorm-eter- to ob^irve- the levCels, alld keep them adju{ledX by mealls of the double hoolt applied- zear the middle of the lzoiler, atuci repreferltd itllX til-e Iediool on the litle TIJ, at the lowellnoIt righQt harld- allgle of t-le plat@.

TheXpyrometer tz;aving beetl adjuIled ill the mallner here de fcribedX by giving fufficiellt time for thc Randard pwrifms-aIld

J XQ(i



Mevpremen! f a BaJ2-orz Houniv-Eleath. 47! mod to colltPraftt to the true Seezing temperaturey as was eafilly Bnosnrru by tlle wires- becomizg perfeAly fixed a2ad Rataonary avith lzgards to tlle ma-ris; the i¢e svas theIl removed from tlle copper trou;ll ; atld the fime betng filled witil-water }early OIl-

ie beily the ebullition was completed, and lfiept upX by;neaase of t!he lamps now lighted for the purpofe< alldi nipped inl;; undernentll-. .'

Tke expaIlfio] allfwering to rthe X Soo betwweetl Deestng a:lld l:oiling, was now rrleafured by working with the micrometer. ficlew uatil the biKeAioil 2 of its: vira with thoNe of th-e mark was agaill compIete 9. the obServer at the fixwed microIkepe taki£g alfo eIi)ecial care a1-1 the -while to keep ho-$bifeEtion perfiEtly accurate. The rlumber of rev-olutiota-sy regiftexed by the num°* lJer of entire diviElons that the zero o£ the circular- kale llad departed from its dart or illdex, atld-alSo the val:ue of any frac tollal revolu-tiota; regiRered bf th-¢^diviIionvs on the head ilw

. . .

tercepted betweelu zero and ts proper dart> *vere thexl notedS as expreAetl itl the firll columtl of the fitlVjoilled table of>- experi mellts S svhich requttes- no other explarntloil than urhat is tl-lereitl itlfertd allcl whwh has lJeen extelzded purpo-Cesly to-

* o

fisew at one view from infpeEtloniot-lly, llow much the- leJlgth of our baSe svould- 11ave been aiRSetda iiS meaSred w rllefe metals refpe&;ively ill temperatures betweeItl 3ao alld-6z9.

AI1 the expetirnetlt4 were repeatell at;le;iR twicg .a-tild fonae of them three tinnesS ts@e-pt the flaladaxl Rale atld glaSs peIl-

* This tbi@&ion of the wires tzzay: aIvsays be made - to a great degtee of prec;^ fon^j by one >;ith a toXel abSy good $y¢7 and accllllemedt to obirvations of this Sorto I havei m7felf repe.iteclly atijuRed the tlires eigtat or terl tsmes .rllnniIlgv^allozbing

another peIXr to rcad vS and.unadjvR cach tirlle without the me?.n->difference. exccedlIig oIle>bwlrth;of a disi;fioll of- the lleEada whsch i$ only z;4o--E5tb pat o} an isch.

d.ul.rllu;



<N S!z2jor-GenervI RoY9s 24acout of tSc dtlltlm roclX svhoft expanfiotls were only tried once. The dS fere<c«e of a fesv diviElons St)etnveen tlae mean atld flextremes oa

t>-he heat of X 8Ot bniIzg,;in things of tilis fort, of 1lo itnportance? it svas judged wlaolIy vlatlecd^ary to a-tlm at; a greater degree of precifion ;11 repeating them oftenbr. 3By referrilag to the table,

articularTy that colulmtl containing tlle expanvfiolls ollione foot by It80°, it 'ill be perceivedS that tlley are ullifo-rtnly a fmad luatter leSs than svllat shas been alElgrled to the IRame metalc rezpe&ively, in the experilnents £orrnerly fallHude-doO

Ull^mafe deerun4sazog o8 he lergxh of the Bayre on Hounnowt Heath.:

In the ;former part of thls- paper, we have uhad occaClon to fpeak of the feven firR columns of the general ;-table of the baSe, alld the titIes at the tops- of t-he others re- EpeEtively ferve fufficielatly to explain thofe towards the right_ llarld; the expani:iors of glafs above, atld its contraAiorl below 62O, contailled in the eleventYl ;{nd tvelftil colulnns, being deduced from the tecetlt experimerlts with the pyrometer.

- Feet.

wrrke hyppthenufal length of the leaSe, as meafured by 369X92552l glaSs rods of twenty feet each +4.31 *-feet, bfeing-the dRance fbetweell tile 1aR rod alld tlre certter of the nortllWweI} pipe, has been {hewll to 13e - - 27-402.82O4

rIze' redu£tion .contained in the feventll wcolumiuL

of tlze general table to be deduded is *0 * o.oy

:E-Ience the apparent length of thetStSe, reduced t.o the level of the fouthcaRextremity becomes 2740Z.749-o

The



AMedJtireane of a BvSfe on Hounfosv-HeatI <7 Ftet.*

The apparetlt lea-gth is to be augmented by the excefs of the expalaflon above the contradtioIl oft the glafs rodsS cozatained in the thirteenth colultl of tlle gezeral ta-ble = 4. X 867 inches> reduced to > ahe heat of 62°, as llas been ufually dolle iil fornlers operatio] s of tllis llature . e 8 o t.3++

Tlle apparent length is farther to be augmeilted lby the equation for 6° difference of temperature of the llalldard brafs fcale between 62° and- 68@> tllis

. .

laI} beitlg the heat in which the Ierlgths of the glafs rods wer.e laid oflD-zc>. 335a illches, as deduced from the experimctlts with tlle pyrometc:r T 69 4f)J

..

Hellce *veihave the- correEt length of the bafe in - the temperatEure of ff2° reduced to the leveI of the ]owermoR extremity near Hampton Poor-houSej 27404,7v923

This lafl: length requlres yet a fmall reduEcion for the height-of this lowerlmoR end above thes meall level of the fea-, fiuppoNed to be fifty-four- fretS or nine fathoms; , 0 , ra.07oS

_

Hence the true or nItimate length of the bafeS teduced to the leveL of the feae and making a por tion of the measlj circumferencix of the earth

%.e Decomes v * . - 0 274O-407:2- 9

Aks fome; fma-ll degree o-f ellcertaintye remains with regard to fhis lall reduAion>> it may t10t be itnproper to fay yet a few words on tlze piinciples that Ilav!e becxaJadher-ed to in 1naking dzc computatiol-<. It will be rememberedj t}watv the m@afure- ment was- rnade 32 feet abourej the furface af the l¢ath9 that beingw the IzLeight o:f ttle Aan£ls ;Xvilereon tilc rods were placed ei

. allXd.



4 758 orv OrZernl F<oYas XCC§:7Yt1! < t°he

a1ld that tlle teleCcqpic fptrit level gave a deAcetlt of 36.I fe6t frot-n the losvelrwzoR pipe to tEle ftlrfice of fum^ner water in the Tllalnes at tIampronQ tRlle accurate fe&totl of thW r;iver lately pul>)lit;hed9 gives a falL of I3.33 5eCt fir3-X nZptOll t0 the 1evd f loxr nvaterprillg tides at lIlesvorefl. :Noer 1thefe*t1aree beilog adcle:l to<gerlael^ vve havte LlesLrly flftyiitilree feet for the height of tile [afe above ItievrorthX Having, had no irnmediate mea;rls of determitiiag v-llat real diSereace !tS-lere flnay ibe betvveen Ifle- worth atld lovv water fpriwg tides at t11e mcutll of -the Thame$ (for inallce at the5EX[opelor the Nore) I have gfuppoSed that }fiw11 to be about Neven iNtet, fo as to make -the total defcent fixty feer. No-t, fitEppoEllg the Epl itlg tides at the Nore t0 riSe eigh ;;teelw:feetn i:Eg accordingteM. DE LA LANDE'S method, we de- dud olle st:hirdiefeighteen v-ZzO fx feet from fixty, we Ihall have fifty-four fee, or tlitwe fithoms, that the meall furEace cfthe fia is below tlle meafilredi-a-feg MJbetller -this coluclu-f1on be ?e-rfeEtly accurate Qr El10 iS Of 1l0 1nOmenT, ;t1Ce a svhole fathom of sdifferel1ce fatld I apprehend vve are n-ot fir-ther frcotn the truth): does not vaRry the reduEt^iotl quite one-tenth of an irsch. The reduced bafe Elas therefore beell found by Xthe follosvitlg ana- alogy: as thevmeatl !femi-diarneter of the earth (fuppoSed here to be 3492;9I S fathotns) augmellted by nine fathoms is to the mean felni-diameter7 :fo is the meafured baGe 274o4.792s <to the redu:ced bafe 27404E.72rg at the level-of the fea It will doul)tlef-s be allowed, that infinite pains llave 13een taketl itl the field al-wil otherv^7ife, throug;houl: tlle whole of this operatiotlS to .--obrail1 a juR conclu{;otl; but as the tuoR accurate nweafuretnel1t imagil1al31e is Rill more liable to err il1 excefs tilatl in deSe2 we will throsr away fome uSeleIs decitualsX arld-eIlablith the ulti- -nwate length of ;the bafe at 27+oA feet and feven-tenths,

Genesal



{ - - - -

sving the relative heights of the Statiotls alDove the fouth-eaR extremity Ilear ISamptoll If tlse HypothenuSes, alld the CorreEtion for the Temperattlre of the Glafs Rcvds; tailPed in the heat of 62°.

5 | 6 7 8 9 | lo II | IZ | 3 14

I w w # _ * *

ltightS umber Temrrature. CorreAion for tempezture.

Total aCcellt. 'oftllellypo- °tf r°tdS' ObServed ' Excefs Expanf.on Contradt. tCorreEtlength - f thenoSes. f et eacl nzean of or defeEt above 62° below 62°^Dierence. 0 t ypotll.'SeAions. e 1 60therm.from62°. + apprlelg.-alart leng-

* _

,l

-a1 RoY§s Sccoant of the MeaJSuremenz of a BaJeg on Houn{low-Heatll. 479

Fnt

z.o7

' *925 7

t.8 5 ) ?3s '*495 s.ob5 *975

D.29s

'e945 5,.9os

)e725 sS55

9.6Xs .03s

Co4°5 3.685 2 e 845 2.405 2959s t465 ;*I95 5 58S 3 535 ;.025 )@}35

Feet. - Feet. 0,OC00 I 2

o.ooz87S

0.002875

o.oo5R8N8 ° oo 7 1 I + o.ooo48g

soooso8>s o.oo706 g o.ooo3g3 OeOOo36o o.osooog

Qs00 I l 68 o.oooS8 1

92552 I

3 3 3

3 3 3

3 3 3 3

3 3 3o 3o 3 3o 3o 3o 3o 3o 3o 3o o

3o 3o 3° 3o o

3o 3o 3o 3o 3o 3 3 3t 3o 3o 3 3o

Inclles

+ o*2909 +0.580I

+0 577°, t -3722 +o.ol86

+ oeoXo3 + o.o6S I

+ o. X 427 + o.2606 + a 245 I

+ 0.02 ] 7

+°.o37z + O. 2 I 7 I + 0.2823 + o*2O47 o.o46

+o.0651 +0§O713 z O.OI55 o.28Z3

+o.z-637 +o o4O3

+ O. I 3o3 + o . 3 6 6 o + °*4839 o 3629 f o.zlog +0xI I 79 + Q. lO86

Inclles

-O. IOZ4 -o.o46s

-o.o403

-o.o86g -ol7gg -0.155l

{nches Ffet.

29+ o

7 4

80 7 t 80.6

74bo 62 6

o 5867 60.5 63e3 64. I

66*6 7O4 69 9 62.7

60 7 63.2 6g.o 7 I . I

68.6 63.5 59.2 56.2 57.o 64Ft 64t3 62.5 71.

7 5 63.3 59^2 66*a 738 77*6 737 68 8 65.8 65.5 6X.5 594 55 6 55 I 56.x 58.4

J 58.z

o

+ 9§4 + I8.7 +18.6 + I2.O + o6 - 3*3 - ,5 + 1.3 + 2v1

+ 4.6 + 84 + 79 + o.7

- I.3 + I.2

+ 7.o + 9.I + 6.6 + I.S - 2&8 - 5.8 - 5O

+ 2.I

+ 23 + 0.5 + 9vx

+ 8@5 + I.3 _ 2.8 + 4.2 + IIz8 + I5.6

7

+ 6.8

+ 3.8 t 35,.. - os

_ z.6 6.4 6.9

_ 5,9 3.6 3.8

lon555 O . ooo 7 45 OsODOI9 1

Ov002222 o oooo73 0.0 I 4439 0*000 I 69

I o oooo36 0I0029z2

L 0.000452 o.ooo 1 35 oooo7bo oooo2O8

o.cGooo63

o.ooo x4 * o.oooos 7 t

O9OOI228 > o.ooooR8

0.00O024 O . oooR 9

b o.oooo24

O.OOI228

o.ool6S3 o.oO4-57 I o.ooog8S

; 0.000192

o.ooo238

6 °.oo I 34 I a.QOl I68 oeoooo36 o.cozo4g

3.42 5 3267 9.88 3 7I5 )@855 9 735 9e595 3.So5 1

++55 3.465 3+935 +.46 5.7 25 6.905 6.715 8.28

o.o86g

-O.OI55 _ o.o807 _Q. I985 -Q.2 I 40 -o. x830 -O. I I I7 -O^l I79



d o > | 5 2*92 5@735 0 0071 Ir :0 62 6 + o 6 +o.oE < = ° > eo o*76 | - t 6*495 o.ooo48g 30 58e7 - 3*3 cd °; 7 I@t 7 8.obs soooso825 3° 60.5 - z X 5

5 v g 8 2.9l I0*975 o.oo7065 3 63e3 + 1.3 +0e04C

O ^ £ 9 _ _ .68 s0 z95 ° °°°393 1 3° 64.I ' + 2v1 o.o6w

; Om : 10 o.6S - xoegAs OeOOo36o e 3o 66*6 + 4 6 o.14t

o g = | | - oo4 1 0.905 x oooooog 30 7 4 + 8 * 4 + 0.26C c: . O IZ - - : ItIS 9e725 QsOOIl68 3o 69 9 - + 769 +a24s

;4 S 13 o83 - - 10-s55 10s555 0s000581, 3o 62.7 + o.7 +0.02]

av d S ] I4 - ° 9+ 9.6Xs ! O °°°745 f 3° 60 7 I.3

° e IS Qe42 - - I°I°35 r aOXI9 I W 3° 63.2 - + I.2 +°-°3

^- I 6 - - I .63 82405 1 0*002222 3° 6g.o + 7.o + 0.2 I ^

g - s 17 o.28 - - S.685 ° °o°°73 3° 7I. I + g.I +0.28t

, g v t8 4 I6 _ 1 ze845 > O*OI4439 3 68.6 + 6.6 o.Xox

Q n ° I9 - - 0-44 I 2@405 : s O*OOOI69 3° 63.5 + IeS +0,04( ,< n S 2 O.I9 - - I2@59 J o oooo36 3° 59.2 - 2&8

a °= 21 1.87 _ _ 14465 0.002922 3° 56.2 5.8 ! ¢; 22 °;73 - - I5*I95 w 0^000452 30 57*° j - S o c ¢t = 23 ° 39 - - IS 585 4 O.000135 > 64Ft + 2.I +0.o6

t = 24 °w95 - - I6v535 °e°°°76° 6 30 6463 + 2 3 +0§C)73 u X < 25 0*49 _ - ]7*025 oooo2O8 3° 62.5 + °95 tO OI

uD W 5>; 3 26 2@ll- 19@135 8.5;8 o.oooo63 so 71.s dr 9.1 +0.28: 1x E

< 1 27 - - 0.7I 18<425 0OOO x4 30 7o 5 + 8@5 +oz-6 o = | 28 0.245 - - I 8467 * °*O°N57t > 3° 63.3 + Ie3 +0 04< < 6^ 1 29 I.2t -- T9Z88 O9OOI228 30 59^2 - 2%8

= o 3o _ _ O.I65 I9=7I5 $ o.ooooz8 3o 66*2 + 4.2 O.I3(

¢ 31 O.I4 - - I9.855 0.000024 3° | 73.8 +II.8 +o.36< @ 0 32 - 0*lz I9-735 ^ t °°°349 " 3° 77.6 + I5.6 +0.48

1 33 oXX I9.595 b 0.000024 30 737 + I t 7 + 0 36

ng 1 34 1.21 - - 20.805 0,001228 30 68 8 + 6.8 *0.21<

^r | 35 X4os - - 22 21 0.001653 3° 65.8 + 3.8 +OxI I

o = 2 36 2 34 - 24255 - ooo4-57 I 3° 65.5 t 3.5 + Q. lO'

tt i 37 - - 1*085 23.465 o.ooog85 30 61.5 . - °5 e < 38 °@47 - - 232935 o.ooolgs 3o 59 4 - z.6 < X 4 39 09525 - - 24.46 K o.ooo238 3e 55 6 _ 6.4 t 3 43 40 I.265 - - 254725 ; > 0,00I34I 3° 55,I ' 6.9

| _ i 41 I18 - 26.905 a.QOl I68 30 s6.x - 5 9

v w 3 42 _ - * I 9 26&7 1 5 oeOooO36 3° 58.4 3.6 a Q n 43 In565 - - 28.28 o.cozo4g ; 30 58.2 - 3.8 / oW = 44 s485 - - 29*765 - 0.0O1845 3o 57e3 4-7

t ° D 45 Q@24 3°2°°5 O o°o°s5 30 60.8 - I.X

*; r 9 46 1.26 _ _ 3I.265 I2+130 o.tol973 ;, 20 65.3 + 3w3 +O.o6 F ; J 400 ft

. S_ " _ W , , , . . , , ., _

4o.44 9X175 3In265 31.265 0§071401 92552I +5§984 .

Hypothetlufal letzgtll of the bafe contaitlillg 1369 92552 glaX rods of twenty feet each + 4.3I feet,

fl RedUalOn COlltAiLlCd in tllt ftYeAth COlunlI] tQ i fubtadedX

Total apparer-t length of tile baCe reduceci to the level of the fout}w--eaR extremity, Add to tlle appal-eilt lel<,atll tlle difference between the expanfion of glaEs above, and the contraEtio

colltained ilo the tlli rteellth colurnlu _ 4* z 8 6 7 inches = Add further to tile apparewlt lellgtll the cquatioll for 6° differellce of temperature of the flandard brafs fcal

68', the heat ill wlsicll tlle glats rods were laidotf=2O.3352 illches,= -

CorreSc length of the bate in the temperature of 62°, reduced to the lewl of the lowermoR extremity, ReduEtion for tlle heigllt of the lorver end of tlle baSe above the mean level of the Sea, fuppoSed to be 54

| True lellgth of tlle lafe l-educed to the tnean lefel of the fea, _ _

R r r \-QL. L-XNVt



-s w -f s ) -& *92552 I

|_ __ ._V_/1 0 *__1_ l _0 _ S l E1 _ ,, _ U S _iW _d - ' b + -

) ?3s '*495 s.ob5 *975 D.29s

'e945 5,.9os

)e725 sS55

9.6Xs .03s Co4°5 3.685 2 e 845 2.405 2959s t465 ;*I95 5 58S 3 535 ;.025 3@}35

3.42 5 3@67 9.88 3 7I5 )@855 9 735 9e595 3.So5 1

++55 3.465 3+935 +.46 5.7 25 6.905 6.715 8.28 9*765 o.oo5 I.265

o oo 7 1 I + o.ooo489 oooso8>s o.oo706^ o.ooo3g3 OeOOo36o o.osooog

Qs00 I l 68 o.oooS8 1

O . ooo 7 45 OsODOI9 1

Ov002222 o oooo73 0.0 I 4439 0*000 I 69

I o oooo36 0I0029z2

L 0.000452 o.ooo 1 35 oooo7bo oooo2O8

o.cGooo63

o.ooo x4 * o.oooos 7 t

O9OOI228 o.ooooR8

0.00O024 O . oooR 9

o.oooo24

O.OOI228

o.ool6S3 o.oo4-s7 I o.ooog8S 0.000192

o.ooo238

°.oo X 34 I a.QOl I68 oeoooo36 o.cozo4g 0.0O1 845 o.O00055 o.oQI973

o

3o 3o 3cz

3o 3Q 3o 3o

3o 3o 3o 3o 3 3o 3o 3o 3o 3o 3o 3o o

3o 3o 3° 3o 3o l 3o 3o 3o 3o 3o 3 3 3t 3o 3o 3

; 3° 3o 3o

: 2O

, l369+

62 6 5867 60.5 63e3 64. I

66*6 7O4 69 9 62.7

60 7 63.2 6g.o 7 I . I

68.6 63.5 59.2 56.2 57.o 64Ft 64t3 62.5 71.

7 5 63.3 59^2 66*a 738 77*6 737 68 8 65.8 65.5 6X.5 594 55 6 5s @ I

56.x 58.4 58.z 57 3 60.S 65.3

+

o 6 3*3

5 .3

2v1

4.6 8.4 7 9 o.7

+o.ol86 -O. IOZ4 -o.o46s

-o.o

-o.o86g -ol7gg

-0.155l

o.o86g

-O.OI55 _ o.o807 _Q. I985 -Q.2 I 40 -o. x830 -O. I I I7 -O^l I79 -o. }458 -o.o37z

+ oeoXo3 + o.o6S I

+ o. X 427 + o.2606

+ a 245 I

+ 0.02 ] 7

+°.o37z + O. 2 I 7 I + 0.2823

+ o*2O47 o.o46

+o.0651 +0§O713 z O.OI55

o.28Z3

+o.z-637 +o o4O3

+ O. I 3o3 + o . 3 6 6 o + °*4839 o 3629 f o.zlog +°I I 79 + Q. lO86

+O.o682

lon555 - I.3 + I.2

+ 7.o + 9.I + 6.6 + I.S - 2&8 - 5.8 - 5O

+ 2.I

+ 23 + 0.5 + 9vx

+ 8@5 + I.3 _ 2.8 + 4.2 + II 8 + I5.6

7

+ 6.8

+ 3.8 t 35,..

os

2.6 6.4 6.9 5,9 3.6 3.8 47

--u I.X + 3w3

2sI30

3 Ix265 o.o7 tiot + 5.9890 -I .8023 + 4* I 867

taitlillg 1 369.9S552 X glaX rods of twenty feet each + 4.3I feet, :olUrllI] tQ i fubtadedX

27+o.8zo4 o.o7 I 4

_ *, , ,

274°2-7490

o 3489

.6946

27404s7925 o.o706

2 7404*72 t9

Suceci to the level of the fout}w--eaR extremity, - _ fferellce between the expanfio}l of glaEs abovey andr the contraEtion of It below 6Zo,1 1w _4* z 867 inches = - - I + he cquatioll for 6° differellce of temperature of the flandard brafs fcale between 62° alld l ,ds were laid of-O.335z lllciles, = - -- _ _ J *

perature of 62°, reduced to the lewel of the lowermoR extremity, - - r end of tlxe- bafe above the mean learel of the fea, fuppoSed to be 54 feet or 9 fathoms = -

he lnean lewl of the Ra _ _ _

'rable R r r



- -

tevolutions and parts of the A&ualexpanfion inparts of a micrometerfor inch by 180°, the revolutio

D:Ecriptlon of the Metal Rods put to experlme£t. the expallSon being divided by 32.o6. On five feet.

_ " 111 -- " 0 . _l _

By s80 By 1°. On 5 feet On I foote Ontool

_ _ I | | * .

Rev.Pts Parts. Sn In In f Sllppefed to be Hamburgh plate hrafs; lexlgth ^ r i

1 4zXS7 inclues, or 38568 feet; breadth o55 ̂

Standard brafs incll; thicknefs oS5 inchi and weiaht Ilb. e 7 t r ¢ > 2C! 6t IO.Tg¢ OeIIItZ2 o.o22R646 z.2z6Ad 4 {cale. lo! os. 1ts expallfion was Mea1ured by 25.47 X}JX / S < /s

revolutions of the mictometer; whereforethat e ^ on five feet would have been meafured by - J

nglifX] plate [ Length five feet; breadth o.g illclz; tllick-1

brafst ill form 4 nDeifficoitl5frollnchts; thinneps tg be kept fre5e2from -t 36.41 20t1% 0.1 I3568 0@o227 l36 2.2713( warpingt

f:nglith plate { Length aSse feet; breadthI.4ixlcll; deptll I 5 brafs, in form 4 illch; weight 8 Ibs. 3 oz. Perfeflcly ftrong alld > 36.45 ao.zMs o. x 13693 o.o227386 2.2738d of a trough. fraightf - - - J

Length five feet; breadth os inch; thicknefs Steel rod. 4 o.3incll; weig t 21bs. 72°Z Madefromthe X 22.02 i2. o.o68684 OOI37368 1,3736E

very ime bar witll tbe clzain, X J 8 Cafl iron f ldength five feet; each of itsfides 14 inch; ) t

priEm l and wYelght ll lbs. g oz Cut fron the fame t 2}.34 1 I.w6 o.o66s63 0*0133I26| 1v3312( red wlth the fiandard priEms of the pyrometer, J Length five feet; ;BitllS ilth diameter;

§ Glafstube. lweight I lb. x X oz. Drawn from the fame} 14.93 &.1E |oo46S69 o.oog3138|o.93I3E pot of metal with the meafiring rodss | J F .

Fr Lengeh 40*44inches, or 3^37 feet; mean dia- 1 > g meter iix-tenths of an inch; and weight X IbX 2 e

. 2 os. It had been applied for feveral years to a | t olldglafs rod.fw clock. Its expanfion was meafured by 10.46: > 15 54 8eX oJo48472 D 9 944t 9 944

rev o l u ti o ns o f the m icrome te r; whe refore that | | t k on five feet would have been meafured by - J

MajorZGentral RoY's Xcvo28 of tbe M¢r 48o

Table of the Expallfions of MetaIs, deduced from experiment



- -w - 0 - - - - | - - - u | - | - w - ^- - -

riments made with the MicroScopic PJrrometer in April I785.

tarts of anl By ° of FAHRENMEIT the expanfion is Bafes of 274co feet of thefe meta

>6. would expand.

| r _ S _

Lt.

Mev0arement of a BaJee on HouIlRow*Heatht

I'

On IOO ft. 01o t foot. Iofeer loofeet. 400feetJ 600feet. I 000 ftt By I . By IO°. By 2 °. By 30°.

[n In In. [n. In. Ilz.

67.7876

6g I576

69 2I24

4Is8I24

4°@S52

28233 I 6

11R. In. In

0,OQI 237

0.001262

0.00 I z63

o.ooo763

oeooo74o

0*0005I7

IoI*68I4

03.7364

o3.8T68

62.7186

60.828e

4224974

4423058

z.za646

2227 I36

2.27386

I 37368

I 33 I 26

o93 T 38

otg6g*

o.o4g48 0*07422 s.38938

3@45788

3.46062

2.o9062

z.o2760

I .4I 658

o.oool23;

0,000 I z6z

O.OOOI 263

o,oooo763

o*oooot40

O Ot:)COS I 7

° °I231

o.ol z6a

0.0 I 263

o.X763

o.oo74o

O*0o5 I 7

oloo539 0.oooo539 °°°539

0. IS37

0. I 262

0.1263

olo763

oo74o

0.05I7

33w8938

34@5788

34@6o62

20.9062

20.2760

I4@ 1658

I4@7686

o.o5048

oJo;:52

o.o3O;2

o.ozg60

o.oro68

o*Xt56

oO7572

olo7578

o.o4Sa8

° 444°

o.o3soz

vo3234 oos39 I.47686



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w:, ,,, ,% s * ' I 2t - 4 'i. !"?,J.1X+ '/ / - V

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|}%4 *EZa Sw^60 8; 8rF wg ........... tS> \ v !2 .re D; /, *fiw vere *@ j \> fH!* *Xe

|Xf<S'0DX{U@By -8l; '; DD-1 'Sod * , ,, {.1/f * w-E 1 @ 0f/a*s 44w4-$>44SS si** * * § w r Z . *. O* . *._*_@*X*_.wi W9 *; 4 *,, * ;,,, K . ,,,,, , | I 0.sqw::s,:,.ws s.N ,t;" 76e ^;; ................ * r t t a t # wh .. t s.0**z:.t\ ...................... ,&e 6' S 'So,dr- t * o -_@ ^ !'1.'''S' :' ' ' /'' o- :. - s :; ,^ . . 1"''t ' ' ' '' ...... ' ''""- ''' ' '''X' """" ' ''" X O ;''"S' ''. z - '"''' ' ; m ) .vs oZg X 4'' 'S' %' ' ' ' w \ # '\'+Bt*' t fs R' o."' -"t"*Xr'T -4't ;'

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KASE meQuwd on HOUN5L(S HEATH in Summew 1784.+

., , . ........ .. . , , , , ............................................................................................................. , ,

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Holdfaft for dme l*End

S Chain.

i

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Appa:rwtw f (he

lld:nd of (he Chain

tof dkereal dinons.

-

- -

-

- - - - -

- - -

-

-

E;ide Elevation oE ffie Card 8tand a

rr D - ----- - - - --- ---



[ l l l 5 ' '- -.-.- . ._._ _T. ,.,., _ ,_.,,

Xor thfe @ESCRIPTZOW and XPP£ICH TI00

t *s

Plan of Ihe l0Link of lie Chaxn in iX originzl State.

End piece of the laLinlc in its altered (Itllte. Plan of the Crofs joint zt evers loiLin}

?

Ekvation of dlelnLinkin itg ariggnal Stzte.

2 3 5

- -

Difpo{ition of Serenteen Stands for the double MeaMurement wsth the Chain gnd Glal Rods.

v Z ..................... .............. .... X " " ......... T ., .s .... =x s .s ... 1

Top of the Card Stand.

E;ide Elevation oE ffie Card 8tand

rr D - ----- - - - --- ---

End Elevation of the C ard Stand.

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

W

¢11vs1lE1 1T1slX11'SV1 tEElllnlllllllulllzlmllvllllllllrulllllllllrllr

S "



a ' ' ! l

ll

Ae@ESCRIPTZOWand XPP£ICHTIOWof the&TEEI CEiSIX.

Plan of Ihe l0Link of lie Chaxn in iX originzl State.

Plan of the Crofs joint zt evers loiLin}. End pieee of the 1d Link in its altered State d St**.

.

?

Ekvation of dlelnLinkin itg ariggnal Stzte.

/2 *98 o 7

It wsth the Chain gnd Glal Rods.

ii

AppAratus for

(he laft End

of {he Chain.

End Elevation of the C ard Stand.

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

- -



Evr t/ve DESCRF7570W a^ZzZ SPP£ICX7tffi0X of a

t I . . .¢T o3..t < ., t<w. : X

Subdirifton of e Ground of one Hypofhende of 600 Feet into 30 Rod Lcngths,and nwelihod

° X S 3 + J 0 7 0 9 o n I ' ' } . , I . , ,

2 d or tniddle Rod .

;nas of fie ROas in Contact 4 of thereal dimenfions . Elearation (he RoAs seen etLdwi.

Elevatbn of dveTripoa.

Bonmg Teleftope .

e4 B onisLy



22V a^a,/ ilPP£ICX7tffi0X of fSe >QEAE AtOWA; kc.

t I - --- .+ _ _ - ; _ t . e . l. = - w _ s_ _ _ __ x

o Feet into 30 Rod Lcngths,and nwelihod of tracing the Line throug31 the Air bymeans of the Boning Rods .

- * - - * - ^ @ v *o o o e * e * o o v w w w * s * @ vo Pv v e - - - v - - v - vv s * ^ * - ;e s e B * o * ^o . - v - * * . o v B . w 6 .......................................................................... * * - . * . w * . w - w w - - v - . - * . ^ ................. ^ e ^ . * . ^ * . e . * o * r - - . * @ . @ o *4 X . . e * * - o . * o . ^. ** . *s ^ 6 *.o *s . * *. - * - - e - * - - . - o v s v + - - v - * ^ * - r P w ^ @ - - w w

0 9 o n 2 zg z4 5 6 g tO ? 2 so@.

l l l l

2 d or tniddle Rod . * A

Elevation of the Ends of the Rods in Co Elearation (he RoAs seen etLdwi.

Hari20ntaz Clap .

Bonmg Teleftope . s= J v

w J

B onisLg Rod .

iL_

- \

-

-q--

S

- -

- -

cc -

c

e

- -

x



f l l l

ztvzow.Xrasz. Z .I X. Tab .,

n e ans of the B oning Ro ds .

* * . * - - * - - - e - * - - s - - - - - - - - - - v - * ^ * -

ZZ to / 2p ,

1Q OI right-harli Rod.

Blevation of the Ends of the Rods in Coincidee.

Plan of the Tap of the sa {hewing the Gerooares for the horizontal Clamp + of the real di:menfoans.



'S = ---- ' ' T S

Subdirif

1 i j ' £

S ecion of Me Pipe &ViReel termiILating the Bafe

.X. Elevation of the Enas of fShe ROas in Contact 4 of the real di

T Y

Verial CLp.

2 L !1 I; il jl 1 Iil lil ililjilli} jillill!,,,,l, l 1l ,l, ,j

h 1 l l ,



. t - _ _ _ _ _ . _ . . . _

X ' 0 ' ,\ A W t ................................................. a:N. T'_ C

Subdirifton of e Ground of one Hypofhende of 600 Feet into 30 Rod Lcngths,and nwelihod

° X S 3 + J 0 7 0 9 o n I ' ' } . , I . , ,

c

l v i ' ' " w


;nas of fie ROas in Contact 4 of thereal dimenfions . r Elearation (he RoAs seen etLdwi.

Elevatbn of dveTripoa.

r taD

Bonmg Teleftope .

e4 B onisLy

I q E>ai:ntea ]

cap 3



w fs - S--;-S 7- T tz-- - - l - 7>- - -

o Feet into 30 Rod Lcngths,and nlethod of tracing the Line throug31 the Air bymeltns oftheBoningRods.

, , , , , , , , l I

y

S s^

B onisLg Rod . -

I ; Pai:llted Hoard.

w 3 v 51saC-

- * - - * - ^ @ v *o o o e * e * o o v w w w * s * @ vo Pv v e - - - v - - v - vv s * ^ * - ;e s e B * o * ^o . - v - * * . o v B . w 6 .......................................................................... * * - . * . w * . w - w w - - v - . - * . ^ ................. ^ e ^ . * . ^ * . e . * o * r - - . * @ . @ o *4 X . . e * * - o . * o . ^. ** . *s ^ 6 *.o *s . * *. - * - - e - * - - . - o v s v + - - v - * ^ * - r * w ^ *

O9 o n 2 zg z4 5 6 7 tO


r lan

-

Elevation of the Ends of the Rods in Co Elearation (he RoAs seen etLdwi.

Hari20ntaz Clap .

Bonmg Teleftope .

e4



, , l I

.

n e ans of the B oning Ro ds .

* * . * - - * - - - e - * - - s - - - - - - - - - - v - * ^ * -

ZZ to y S s^

1Q OI right-harli Rod.

Blevation of the Ends of the Rods in Coincidee.

Plan of the Tap of the sa {hewing the Gerooares for the horizontal Clamp + of the real di:menfoans. r lan

-



Ist olz lett-hand Rod.

| § 1 h 5 lE r *8 BlllWll0l llIYYX

Longitudinal Section of the movealvle End of d S d R in iew real dimenfions .

Longitudinal Elevation + of the real dinledlorLs S

s - _ L

sR UA

I Plan Plan



/ f a X 4 K S 0 O t

| i iSlS hj 5, r BlilWll0l IIIYY 2k 1ll Ilkililililililililill,lilli wIwilililluislwiltlillululli S " IIIt III5II Y 0 [lsJullxillbillulilililil uxls _ itilillxilulilililnvull]

1b I'

,. . |

|

I w

_ ....

,,, t.gzz9EvS'C'XPT7b2ZAst ,oz/iZ>'SZ{txl7''7z92\T!/'t

2'! or middle 1{ot1.

.J'c.*v of' st? .

udinal Section of the moveal,le End of the d Rod and fixed End of (he L in (heir real dimenfions . I

Section acrof's the lniddle of thc Rod

* oft the real mearons.

La

$

-r X s z t to v

of j* wtt-s f oXi l

;r5 fmv

d :b



AsAiAiAisiLE jAss, j, ,s,, ,ilAlA1 ill A i 11,, ,1,1 ,,1 . ,|k{XilliliAlAiSAll. I M.'1sLS # Vs 11sfi w ssssi I> ---- w - --- ------------ -- --- ---- iLSb ; siul llLlriiAlliassl>a llki& 0 . .4 i.lL pi1' iA. iA s11Aa

ZO ,{ w177z9,\t !/ z/'t t'' - j^i' st Mt")J) b'

1it ll t; l ! 1 1 ; llij illP !,'11.i' 1 1 1 ! , 1; lli -- .rt t-YsC n -

: '',ill ' .,

>>1Ul,u',ll$4

lq I.,ll,ili.si.l..l. . i.l.it Illlllllll 16ia1s A 1- 1 .-lil lllllltl,il '1lli l>i.4'.i;11

Longitudinal Scetioll of the moveable End of the ^Rod andfiwea End of the 3dR (heir reAl dimfllons.

tion acrof's the lniddle of thc Rod

f the real mearons. w-!wl-||NSlESo

t7=== ---ll-S-Zffl



c

! :,. I Cw

| 5

* X

o

o

1

tD O

.A a m

p

bo ;§

p 3e m.

q ' W

lily I

- -

- -



Ist olz lett-hand Rod.

Z ol z / f

| § 1 h 5 lE r *8 BlllWll0l llIYYX

Longitudinal Section of the movealvle End of d S d R in iew real dimenfions .

Longitudinal Elevation + of the real dinledlorLs L

s- Rod 1 ? t 1 l 2&RM

sR

Plan

3

Front Eleration of tlle moveable End.

zr _ _ ,, 1^ n Rnd f



1I lin; u114 -

La

1 D -

j

| 7

_ . . .

....

. .

[ §^ "1^ h H lE r

111511 1 1111 1T1T 1 1 1111111E111l111 1111 - b ... . I ........... _ _ _ :_ .* Ai _ e iB iSlS h 5, r *8tlllW2llW YY k 1ll IItIIlillIIIIIIIIIIIIIlililti ioilililililluislWlltlillululliii S s iy y 0 i'slxlullxillbillulilililil uxls _ 1111111X11:1111

| HillrlE tHIIIIt ^_irnlt RllfRs millrn _ "<"§"'s'r""'SY"W "V""""""^ . - ria

-

.J'c.*v of' st? . / * 3 8 f S 7 0 9 ^'

oI i f n

udinal Section of the moveal,le End of the d Rod and fixed End of (he L in (heir real dimenfions .

t-{- { / £ tlaXWs J s £ z jo

s of j* wtt-s f oXi

A - rl waS

2

Sa - ' /r *t qc7r ;w S .


Section acrof's the lniddle of thc Rod

* oft the real mearons.



11 'IlllIElllllllllllplllw illullllllblllulllllllll uxls _ ,=llllllIXllUllllllln[u11411111 illllllll]ElllllllWENIA i a

-

.J'c.*v of' st? . 0 9 st n rf .s zW t5 r6 r7 < > 4t .*°

tion acrof's the lniddle of thc Rod

f the real mearons.

,= ,.,_t s S z 1° .

wrn _ =, 2 _§<gX'lvr§|ssvw|wfftw . .

i*t qc7r ;wg.

_


Longitudinal Scetioll of the moveable End of the ^Rod andfiwea End of the 3dR (heir reAl dimfllons.



-

3 4 or r ;,tz t - h vl ll(t ltoeJ .

L oss;itwdinal i; 1 e v atio1l j

dimelAons .

_a=;__- J w S A . . -

p

Plan pl



! X ' § '- ' s H 1+ >r 9 -

Seale to ihe C;enerAl Plttn and Elevations.

|i_j; , ,i , l X, 'idililill§ilil 'i ' i.ii - ll I _=== sil ...................................... ' I' . . ". i.# " Eoo fAw

Ele-

1F--

-

EZlevaiion of the Eye Piece Side .

P<r, GenerAI Plan of dve Top .

o

fElerration of the fiwed ced of theBeriler.

- f k

if F w



Eoo fAwe SEXCRIP>OX ,SV M5E of tAt MZCROSCOP>CPEROMEtER.

PE j<LMS awd EL f5Z2l 7570W5 nf the A{3RKS and EYE-P>ECEs + Sf MG reccC c. _

Mcrameta Mrrofosspe. Fixed Nlicrofcope.

r ^

r - -r - @ I _

__

| _i @ _.

* mQ ; 1=

I, . . . * . I s s Iu

Horisonl

l.angitudinal Seci on of dle Boiler wlth its Slides and dle Sleel Rod as in experiment 4 oP the real size .



At .

l X l t | t

IllllzlllllllllllllllllllIIIIIIIIIIIIIIIIIIIII'IXII'I'!IIIIilllllllllll ll

EfttZn.v.3Zzznr. 4/.I X Tab 2zX . s . aZo

COXXS'rRE'C 7wI0UV yf Me MSRROSCOfPCS.

Eletion af the Micrometer full l;e .

E l s s l l

Horisonl SecSon of e Mictometer.



! | x l-EE i x 5 1- l- , | o

-

Seale to ihe C;enerAl Plttn and Elevations.

P<r, GenerAI Plan of dve Top .

Z 9 .

fElerration of the fiwed ced of theBeriler.

- .= w _



PE j<LMS awd EL f5Z2l 7570W5 nf the A{3RKS and EYE-P>ECEs + Sf MG reccC c. _

Mcrameta Mrrofosspe. Fixed Nlicrofcope.

r r .

> i ' I ! llElilil {ll'fl IlilillAlallillIIIIL

-. S P S -r-

- __l @ I __ __ s _ l_ I | __

I 1wi1!',

I, . . . * . I s s Iu

Horisonl

l.angitudinal Seci on of dle Boiler wlth its Slides and dle Sleel Rod as in experiment 4 oP the real size .



, , . I .,, ......... § *1'

Horisonl SecSon of e Mictometer.

D _ ' _ A

Xee,9

.

-

-

Eletion af the Micrometer full l;e .

l *

ElevaXon of the Spring End of the Bolir. _ ts e == -

s 1F

Scchonall the Line

R

_|11|_



An Account of the Measurement of a Base on Hounslow-Heath. By Major-General William Roy, F.R.S. and...

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Transcript of An Account of the Measurement of a Base on Hounslow-Heath. By Major-General William Roy, F.R.S. and...