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1. lI'ilh 3n n~(fIUrC in Ihe núIJ:~, C. The lub~s are
c..ncd in a II rong IIr.tlchl ruler, a fvollonl:; al whoCe
tll !' are fixcJ 111'0 (¡ghls, 3, 3, ex.~tly perpendicular \O
t"~ lubes . •nd ,.( an e h,igill, hdVing a ¡quare hule,
ti,,.,nld by IlI'u fi lltls of orafs erlJlling eaeh ('Iher al right
all~les ¡ in Ihe l\)iJJlc .,hc, eof IS ¿nlled a I'ery lia lchule,
th, ongh whieh a point on abd wilh Ihe inllrumenl is
d~fa,ed. Thc llIbe is f.llcned on Ihe rub by
mrans of IWOfCI'CII'S, ont wher<of, markcd 4. ferves 10
raife Or deprefs Ihe IlIbc al plcafure, for bringing it 10,
wuds a level. The IOp of theb,lJ and foelel is rivetlcd
10 alill l: ruler thar fprings, one end whereof is fallened
wirh fere\\'s to rhe gre.r ruler, and ar Ihe orher end h.s
a fercw, 5, ferving deprefsIhein(lrument wAen
n:arl)' level.
This inHrument, bowevcr, is yetlefs eommodious Ihan
Ihe follolViog ooc; bee~ufe thoughlhe hules be erer fo
fm. II, yet Ihey IVill ni" intoogrm afpaee ro dm r·
mioe Ihe puiot of level preeifely.
T his iollrumeot eoofin, of an air lcvel, wilh tclereope
fights: tbislevel (ihid. DO2.) is like the lall, wilh rhis
dill'erenee, thal iollead of plainfighrs. it earries a telefeope
to determioe exaétly a poinr of level at • good di(lanee.
T~e relefeope is a lin!c braCs·tube, about fifreen inehes
long. f.lleoed on the fame ruler as the Ievel. At rhe endof
the lube of the telefeope, marked f , eDlers the littletube
1, earrying Ihe eye'glafs aod ao hair horizontally plaeed
in theCoeus of Ihe objeét.glafs, 2; whieh Jinle rube may
be drawo Out, or pulhed ioto the great ooe, for adjulliog
lite telefeope to diJtcreot fights: at the other end of the
telefeope is plaeed the objeét.glars. Theferew 3, is for
raiGng or lowering the little fork, for earrying the hair,
aod makiog it agree wirh the bubble of air, when the io·
nrumeot is !cvcl ; aod the rerel'! 4, i$ for makiog Ihe
bubble of air, D or E, agree wirh Ihe telefeope: the
whole is fitted 10 a ball aod foeke!. M. Huygeos is raid
10 be the firll inveotor of this level, wbieb has Ihis ad·
vanrage, th;t it may be inverted by turniog Iheruler ;, nd
telefeope half rouod ¡ and if then Ihe hair eUI the fame
poinr that it did before, the operalioo is jull.
It may be obCC/Ycd, th~r ooe may add a relefeope 10
~oy kind of level, by applyiog ir uponor parallel ro tite
bafe or ruler, when there is oeeafion ro take tbe Ievel of
remote objtéls. .
Dr Def.guliers eontrived an inllrument, by whieh the
differcoce of level of twOplaees, whieh eould nor he tao
kcn io Hs thaD four or ove d~ys wilh the bell teleCeope.
levels. ot~y be !aho in as fclV huurs. The ioflrumeot
i, as follolV5: 10 the ball e (ibid. 0
0 3') is joio~d a re·
curve tube R A, wirh a very fine bore, aod a fm all
bubble at rop, A, whofe upper part is opeo. Ir is
el'idenr from Ihe make of this iollromeot, that if it
he ioclioed in carrying, no perjudiee \ViII be dooe to
the liquor. which ,"ill alway' be' ight bOlh io the ball
Qod tuhe ~ hco the inll rumcnt is fet IIprighr. Ir the air
at e, be fo (xp,oded \l ilh he~r, as ro drive Ihe liquor
to Ihe 10p uf Ih~ luhe, Ihe cavily A will reccive rhe li·
«)oor, u·hich \ViII come down again aod Cellle at D, or
ne." ir, aceordiog ro the levd of lite rl~ee where Ihe in·
ti rumerot is. as foon as the .ir at e reHlrns to thc
temrerament as 'o he.1I 31,,1eold. To prererve the f:"l1:
VOL . JI. ¡'¡ulltb. 67 ' 2
L E V
degrce of he:r, w'len Ihe difFereor ohfervation! are m~d~,
Ihe maehioe is fi xed in a tin ven'elE F, fiJled wilh Water
up 10 g h, ahove the ball, and avery fltlliblc thermfm:r"
has allo its ball uoder water, thao noe mal' obfe,vc Ihe
liq uor at D, io eaeh experimeol, when Ihc therOlom"rer
U.ods ar thefame height as bdore. The water is pOLTed
oot when the ioUrument is earried, whieh ~ne may do
conveoieotly by meaos of rhe woodeo frame, whielt is
fet u¡¡right by the rhree ferelYs S, S, S, ibid. nO4.
and a lioe and plummet P P, nO 5. At the bae!: part
of the wooden frame. from rhe pieee at top K, hoog'
the plomOlet P, over a brafs puiot at N; M In are
braekel5, 10 make the upright board K N eootioue
at rigltt aogles wilh the hOrIZontal ooe at N. N° 6.
rcprefents a froot vie.., of the maehioe, furpofiog the
fore part of the tin ·ven' l traofpareot ¡ aod here the brafs·
foeket of rhe reeurve rube, ioto whieh the ball is rerew.
ed, h.s two wings al I 1, oxed to rhe bOllom, that the
ball may oot brclk the tube by its endeavour tO emerge
\Vheo Ihe water is pourediu as high asg b
After the Dr had eootrived this maehine, heeooGder.
ed , rhat as the rube is of a very fmall bore, if Ihe liquor
(hould rife ioto the ball at A, nO3 in earrying the io·
Il rumeot from ooe place roaoolher, fomeofit would ad.
here 10 the fides or the ball A, and upon irs dereeot in
making the experimeot, fo mueh might be left behind,
Ihat the liquor would not be high eoough at D, to Ihelv
the diffmoce of the level: rherefore, to preveot that in·
coovenieney. he eontrived a blank ferew, to ntut op the
bole at A, as foon as ooe expeiimeot is made, rhat in
earrying the maehine, the air io A may balaoee that in
e, fo Ihat the liquor (hall not run up and down thetube,
whatever degree of heal and eold may aét upoo rhe in·
flrument, in goiog from one place tO another. Now, be·
caufe ooe experiment may be made in the moroiog, Ihe
water may he fo eold, Ihat when a feeond experiment
is made al ooon the .·ater eaonot be brough t 10 Ihe
fame degreeof cold it had in the moroing; Iherefore, in
making the firll experimeot, warm water mull be m;,:ed
wilh rhe eold, and wheo th¿ water has Ilood fome time
before it comes ro be as cold as it is likely tObe al the
warmefl pan of tllJt , obferve aod let down Ihe de.
gree of the Ihermomerer ar whieh the fpirit H.ods, aod
likewire rhe degrce of rhe water in thebaromerer at D ;
then ferelV 00 the eape at A, pour out Ihe lVarer, and
oarry the iollrument tO rhe pldee \Vhofe level you \\'ould
knO'N¡ theo pour in your water, and wh~n the Ihermo·
meter is COme to the {ame degrc~ as before, opeo the
ferclV at IQp, and obCerve the liquor io rhe baromerrr.
The dotlor's feale for rhe barometer is leo ioehes
lunR. aod divided ioto reoths ¡ fo that fueh ao ioflnt·
menr will Cerve for . ny heighls not exeeediog teo feer,
eaeh tenllt of an ineh anflVeriog to a fOQr io height.
The Dr Olade no allo'Naoee for rhe dcere.lfe of denGry
io rh~ air, bceaufe he did out prerofe rhis maehioe fo r
mcafurioR mouotaios, (Ihough wilh a p,opc!' allow.oee
for Ihe dCCl eafing denfiry of tIJoir. it will Jo I'e,y 11'1:11),
bm r<If heights Ihar want ro be knoIV o in gardcns,
plaototions. and the eoov yallee of lVater, \Vh"e an
cxpcriOlent !h" arofwcrs t_o or three fcer io a difldoee
of twcnly milrs, will render Ibisa I'lry u:eroliaflrumrnt.
10 ~I t Af/il/(r).