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of ,be 0.11, anJ inverrely ns ,he of ,he nem. Firll, If
the bife ol' {he ítem or c)'Jindricíd rube is giveo. Ihe varia·
tion, whcn lee fpirirs are cquillly wanncd, \ViII be direél ly
a1 the capad!y ot lhe b,111. f ar whl:n Ih~ (1'lrils are equilJ.
Iy wd.rmed, and confcqllC.'ndy are eq~l.dly rardled in lhe b~lI,
oftWO diírl!rent thermomc::tcrs, wh.u cver proponían tbe bulk
of ,he (pi"" in one ball be.m ' o ,he bulk of ,he fpiri..
in th~ other ball · before lhe}' \VeTe rarelied, lhe (ame
proponion ,hefo bulks will lIill bear 'o eaeh o,her af,er
Ihey are rareficd. Thus, if one ball is double Ihe 01h:r,
and conf~q"cndy . ,he bulk of fpi, i ts in one i. double ,he
bulk of fpirits in lhe other befare Ih~y are warmed; Ihen,
upon being war01ed equ:1l1y. th~;.f aenfi ties will diminifh e·
qually. Bu, i( ,heir denfi,ie. diminifh equally, ,heir bulk.
wilJ (hll h"ve Ihe fame: proponian 10 eaeh other; or lhe bulk
of (plrils in one thermome:ter wdl fiill be double the bulk in
the other. B Ul if Ihe bulks cootioue in the fame proportion
to eaeh other. after they are fwelled as rhey were before;
Ihe rpirits.mufl f\Vell in proportion 10 ,heir refpeétive b\1iks,
or the fpirits iD one mull f\Vell twice as much as in lhe o–
Iher. Bu, i( ,he rpiri .. fwell ;n ,his proportion, and by
fwelliog fife imo equa! robes io eaeh, (hey mufi rife l\Vice
as high io the tub~ oCone of [hefe thermometers as they do
io lhe lube of lhe alher. And fo, in all other innance~, che
fpirits, upon beiog equally warmed. will (well io proportioa
to their bulk. that is, io proportion' [o the capacicy of lhe
ball that cont::l.ins them. But the heights, lO which they
rife io equ,'¡ tubes, will be as thl: iocrea(e of the¡~ bulk.
Therefore the heights tO which lhey riCe, or the vari ations
iD equal degre.s of heat, wiJl be as ,he capaci,y o( ,he baJl,
",hen !he ,ubes are equ.J. We have here ruppofed ,hat
Ihe fpirits in ,he , o( ,he ,hermome,ers are equall y heat.
.-d qui,e ,hrouglo . In fudilen changes o( he" and cold, i,
",ill i;>e o'henl'ife: for ,hc fpirits in a fmaJl ball lVill be
fooner h.eated quite Ihrough Ihao io a Jarge ooe . And coo~
{equently, i( the heal does:oot lan long eoough to warm the
{pirits in a Ltrge .b:~1I as much as they are warmed io afmall
o~e, .he (piri,s wiJl no, be equally rar. fied in bo,h, and
wiJl no, r"'ell in propoflion 'o ,heir rerpeétive bulks; bu,
thofe in ,he rm. JI ball wllI f",e11 m01:e in proportion ,han
tho~e in ,he large ooe. Secondly, If ,he ball. are equal,
Ihe' varia,ions wiJl be inverfely as !he bafes o( ,he flem•.
Fór ir ,he baJls are equal, ,hen, upon bcing equally heared,
,he fpi ri.. contained in ,hem lVill fwell cqu, lIy; ar,d con ·
· ently equal quan,i,ies ",ill "fe in,o ,he lIem.. N olV
the fpirits ~hich riCe into a cylindric,,¡ (lem are acy!indri–
cal column. But the heighls of equal cyllnders are ¡overfe–
'1 i.. 'hci , bafes: Thcre(ore, when ,he balls are ~qual , and
tqual cylinders of rpirits riCe into the fiems, the heíght!' te
which (hey rife, or the Yariati~ns, will be ioverfeJy as lhe
bar.. of. ,he lIent•.
An unt:Jtrfal fctllf n/ay /J~ mod(, hy rwhich ,Iu va"iat;onJ 01
dijfcrenllhermolJulcn "'OY be comparul wilh one ano/ber.
Let the ball of a therOlometer be pUl ioto water when
it is bt'ginning ro freezt!, or, \l.'hich is the (ame as to he,u or
cold, ioto fnow \I.'heo it IS b('ginning to melt ; and Jet the
place where lhe flui d in the thamo01ct~r (hnds be m.rkcd.
The place where the fluid nands i-o (uch a tt ial is lhe free·
zinRpoiot. Let lhe ball o( the Carne thermomcter be put
ioto water juJl hot en',ur,h to Jet wax, th,u fwims upno ir ,
lH.'gin 10 coaguLue. 1'his agaio is tlilOlhcr. d~term; nale- de
,ree of he?.t. .and ís to pe m~ukt!J uroa the, thermOmtH:f.
VOL . ¡JI N° 89. 2 .
A T e s.
Divide rhe dinance belwcen theCe t\Vo points ioto 110 equ,.1
pan s ; il nd of thc(( pans \Ve cal! a degrce. . Now a
lhermomcrcr often finks lower than the freezing point ; be·
cauCe the colJ is frequ eotly more e dun what is ju!!
'fu fficient to m Water frccze: for this reafoo, the Ccale mu1t
nOl begin Trom lbe freezing poine Thif poiot, therefor¿.
f'hnuld nOl be m2rked o, nor (hould lhe painr where mch~j
wax begin5 lO coagulate be marked 110. In this
which from rhe inventor is callcd F¡,¡reoheít's Ccale, tbe
f,eezing point is m;ukcd 32; aod theo lhe poinl . ",here
melted wax hegios lO coagu1::1.1e, being (1 0 dcgrecs abo ye
it, mu(l be Olarked J42 . When lhe leogth of a dC"gree ti
,hus (ound in one part of ,he 32 .degrees of ,he fame
length are {et off bdow che frecz~ng point. aod as m1ily
{uch degrees as \Ve picare are Cel off above the poiot where
mdtcd wax begi ns to coaguhuc. If lhe thcrmometer i.s
made wi,h fpiri" o( wine, only 33 degree~ need be fe, off'
_or marked a'bove 142 : -and ,hen ,he wlJI begin from
o; 32 degre•• will be ,he Treezing poin!; ' 42 w;J1 be ,h.
POiOl where me!rcd w~x begins to coagulatc; and 142+33-;:
175 degree, ",iJl be ,he l\ighelt po;n, marked in ,he
T he reafon why no higher degre< need be marked iD a
applied (Q a thermometer made with fpirits, ¡s, chat al lhis
degree of heat lhe fpirits wiJl boil, al'ld eonre'1uently the:
thermometer would burn . But ir (he thermometer i:t made
..."h m.rcury, ,he fcale fhould con,.in a' le.n 2' 2 degreos'
from the bottom tO lhe (OP, or 3 2 degrees belew the [le(7
zing poine and 180 "bove il. The heat of boiliog water.,
at [he middJe heigM of Ihe mereury in (he baromcter, ar
in che middli: weight of che atmofphere, will raiCe lhe mero
cury in the thermorueter ro '212 degrees, or 180 degrees a–
bove the freeziog point. A thermometer m..de with me("~
cury will nOl burfi in fuch a degree of heal as this; (or
mercury requiTes a greater ctegree lO make it boi l
In thermometers \\Iilh ruclra fcale, or, as 1hc:y are cal1ed,
in fot renheic's thermonleters , the 'greaten degrce of hea t in
che external parts o( lhe human body tScommonly about 96.
Boerhave inugined tha\ air, ír its heat exce'eded 80 or 90
degrees at mon. \Vol1ld be deflruébve to Ihe Jife of animals.
Bu, in ,his he w.. miftaken. For in !he year ' 73 1,h..
,hermome,.r in Penryltania wa, a' ,he heigh' of 96 or 97;
and in ,he year 1734 ,he heigh, of i, a, P e\el fbu rgh "'as 98
degrees . The thermometer in OUT Qwn d imate is Cc'1rC~ t:.
ver highcr ,líao 78 degr<es, and reldom 10IVer ,h~n 18;"fo ,har
wc may rcckon 48 d<grees 'o be ,he middle ,emperalure of
our airo
T he vari.n ions o( different thermometers. Ihough thev
are nOI equal, may be compared with one another by Fa·
reQ},ei t's (cale. For each degree upon diff(.'ren[ thermome~
ters is proponional 10 their refpe{\ive '..arialioDs; and con·
fequeotly, Ihough in equal heats one may v?ry more du n ¡.
nother, yet e¡eh will vary an equ-al oumber of degrecs.
Thus, .r, upon any gil'en increafe of heat, one thermom:–
ter will \';uy lwice as much as anolher, [hen Ihe ddhnce
between the freezing POiOI and 'lhe point where melred
wax hegins 10 cO.lgol-ate will be twice as great, or 11 0 Je·
Arees wiJl be lwice ;l S long, in one as in the other. Th ~r¿rore lach acgree " ill be twiC"e as long
in lhe former ther–
mom~tcr ~IS Jn the I.uer . BUI by the fuppofilion" one oC
theft lhermometers in a given degru of heat wil! ' lWlce
as much as the ollll'r doe!; and conrtqueotly. Whalf\ cr hcat
raifts ,he former one d('greeJ willlikcwife r¡¡¡re t:lC J,ule:- on~
rlogrte .
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