1000000030

820

H Y D R O S T A T

e s.

plaeed by íl \ViII be cqual in hulk

Ihe part of Ihe

innrument under Wal tr, and

cqu~1

w~ighl

Ihu

of Ihe wllole

inil rum~nt ,

Suppok the W<lghl of the

whale

wer~

4000 grains, then it is evident we can hy

this meaos compare tOgelher Ihc diffmnt bolks of

4°°0 graiosof various f,ms of Ouids, For if Ihe welght

A b. fu ch

3S nI

011 caufe the arreomcter

fink in raia·

waler, till irn furface comes

the middle poi nt of die

/lem 20; and if, afler Ihis. it be immerfed in common

{priog water. and the [urface is obfcrvcd to ftand

of an inch lidow the middle point

~O ;

il is evid. ot

that the [ame wcight of each wat.r dilfers in bulk oo·

Iy by the magnitudeof

of an ineh in the fiem ,

Now fu ppofe the Uem were teo inches long, and

weighed 100 grains, theo every tenth of an ineh would

be one grain weighl ; and fince the Hem is of brafs,

and brafs is about eighl times heavier than water, the

fame bulk of \\'ater will be cqual to

of a grain ; and

confequently tO the

part, thal is, a 3200dlh

pan of the whol! bulk, whieh ís a degrce of exaélne[s

as great as can be defired Yet the innrument is ca·

pable of (lill gremr exaélntfs, by making Ihe (lem or

neek confin of

flat thin Oip of brafs, inllead of one

that is round or cylindrieal: by this means lI'e inereafe

-¡he [urface. whieh is the moll requifite thing; and

diminilb the [olidity, by whieh the inilrument is ren

dered more exaél,

In order tO adapl this innrument to

311

[orts of ufes,

-¡here. ought to be IWO different lIems to ferew on

and off in a fmall hole at

One Ilem Ibould

fueh

a niee thin Oip of brafs, or rather of lIeel, like a wateh·

fpring fet Ilraight, as \lIe have jull mentioned, ooone

lide o[ which ought to be the feveral marks or di,i·

fions tO whieh it will fink in various fons of waten,

as rain·water, river,water, fpring water, fea'water, falt

fpring.\Vater,

6c.,

A~d

t~e oth~r

fide you m,ark

the divifion to whleh

finks

.anous IIghter flUlds,

as bot bath water. Bri(lol water, Lincomb lI'ater, Chel·

ten water, pon,"'ine, mountain, madeira, and I'arious

other fom of wine. But in this ca[e lhe lI'eiCht A on

the tOP mufi be a little lefs than before, when it was

,ur~d

for the heavíer waters.

BUI, in eafe of trying the il rength of fpirituous li·

oquors, a common eylindrie nem will do bell, beeaufe

of its nrength and Ileadirefs ; and this ought to be fo

cootriv~d,

th. t, when immerfed in what is called proof.

{pirit, th<furface, of.the fpirit may be upon

,th~

mido

dIe point 20; whlCh

e. fily done

duly adJulhng the

fmall \\ cight A on the top, and maklOg the nemof fueh

a length that, when immerfld in water, it OIay jull

,o\'er th~

ball, and rife tO

but, whl'n immerfed in

pur e fpiri l, it may arife to the top at A ; then, by di·

, iding

th~

upper and lower parts

20, A '0, lOtO ten

equal

part~

cach,

\V~en

the,inn',II,,?fot iS,immrrfed in any

{ort of fplr:mous lI«our, It wllllmmedlately Olew how

mueh it is ahove or bclow proor.

This I'roof'fPirit confins or half water and half aleo·

hol or pllre fpirit ; thal is, fueh as when pOli red upon

gun powl1er, and fel on Jire, \ViII

bur~

al! a",ay, and

permit the pow¿cr tO take fire, whleh II wIII, and

O,IIb as in Ihe open ai ro But ir the (pirít be not fo

highly reélilicd. there will remain fome phlegm or

water, which will m.lke the powder wet, anJ un6t tO

take 6re. T his proof, (pim of any kind IVeighs feveD

pOllnds twelve ounces per gallon.

The eOOlmon methodof

Ib,~ing

the (pirits in.a vial,

and, by raifing a erown of bubbles, to judge by the

manoer of their rifing or breaking away whether the

f~lrit

be proof or near it, is vcry precarious, and ca.

p.ble of great fallaey , There is no way fo eafy, quiek,

eerrain, and philofophical, as this by tbe arzometer,

"hieh \ViII demonnrate infallibly the diff'mnee of bulb,

and eon(equeotly ipeei6e gravities, in equal weighu

of fptrits, to the 30, 40, or 50 thou[andlh pan of the

whole, whieh is a degree of aecuracy bcyood which

nothing can be defired.

AII bodies expaod with hea!, and contr¡él witb eold;

but fomemore and fome lefs titan otbers: and therefore

the fpeeilic gravitiel of bodies are not preeifely the (ame

in fumrner as in winter.

has been found, that aeubic

ineh of good bmdy is 10 grains heavier in "ioter thaD

in fumme r; as much fpirit of nitre. 20 grains; vinegar

6 grains, aod fpring water 3, Henee it is mon profita.

ble tO buy fpirits in winter, and fell them in fummer,

finee they are always bought and fold by meafure.

has

beenfound,

th~t

32 gallons of [pirit! in winter will make

33 in (ummer,

The expanfion of all flu:ds is proponionable to the de·

gree of hm; that is. with adouble or triple heat afluid

will expand two or three times as mueh.

pon the(e principies dcpends the eonllruélion of the

thermometer, in whieh the globe or bulb, and p.art of

the tube, are filled with a 8uid, whieh, wheo joined

to the barometer, is fpirits of \Vine tinged, that it

may be lhe more eafily feenin the tube, But when ther·

mometers are made by lhemfelves, quickfilver is gene·

rally u(ed

In the thermometer, a feale is fitted to the tubc,

tO Ibew the expanfion of the quiekfilver, and eonfe·

qu'ently the degree of htat, And, as

fartnh,i"¡

[cale

is moll iD efieem at prefent, we (hall explain

th~

con·

Ilruélion and graduation of thermometers aeeording tO

lhat feale,

Firll, Iet the globe or bulS. and pan of the tube,. be

Jill.d with a flu id; then immerfe the bulb in water Jull

freezing, or fnowjull thawing; .nd even ",ilh that part

in the feale whm the fluid then nands in the

tob~,

plica

Ihe number 32, to denote the freezing point : then pUl

th~

bulb under rour arft pit, when your body is of

modtrarc degree of heat, fo that it may aequire

th~ f~me

dcgrc~

of heat wilh your tkin ; and whcn Ihe flUid has

rifen as far as it can by that heat, there place !he

number 97: then divide! the fpaee bctween thefe

~um·

bers ioto 65 equal pms, and eontinue Ihofe dl"fian.

both above 97 and below 32, and

num~er

theOl ae·

eordingly,

, .

This may be done in any pan of Ihe 1V0rld; fer,

found Ihat the

fre~zing

peint is alw,ys the ("ne '" all

plaees. and tbe

of Ihe human blJy d;/Tm but

v"1

Jittle: fo that lhe lbcnnoDlelers made in this mann

ill