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p N E u M
l.;ndles in the bowc1s of th~ carth , where there js little or
no vent , it produces ~.""Ihqfl 'k.(/. anu violent Uorms or hur·
ricanes of wlnd when ir bre ..ks fortb iOlo lhe alr.
An anifici.a! C may be [huso T o¡ke loor
t 5 ponnds of fulphur, and it$ much of rht' fil ings of Iron, and
knead them with commun wi:lrer tnlO lhe t:onfillence of a
pafte: lhis being buried in lhe cround, will. in 6 0r 10
h OUTS time. burH out in fl ...mes , anu cftufe tbe canh to treDl~
ble all around to a eonfiderable d iflanee .
. From {his experil1lent we h,.ve a very natural account of
the fire of moum .JEtoa, Vd uvius, and other \'olcaoo's, they
being prob.bly Cet on' lire at lirn by ~he mixture of Cueh me–
ullioe and Cull'bureous particJes.
Oflh. AIR ·.I1M'_
T HE air_pump being in effeét lhe Carneas thewater.pump,
(fee H yo. o S T ATI e s,) whoever underllands the noe will
be al no 10Cs the other.
Having put a wet leather on the piate LL. of the air–
pump, (Plat. CXLV. fig . 8.) place the glaCs receiver M up'
on the leather, Co that the hole i iD the pbte may be wit~iD
me glaCs. T heD, turning the h'Ddle F baekward aDd for–
",ard, the air \ViII be pumped out of {he r,eceiver; which will
then be held down to the plate by the precrure of the exter·
nal air or atmoCphere. For, as the handle (r.g. 9.) is. turoed
b.ekwards, it raifes the pillon d, io the barr.! BK, by
"'ean. of the wheel F aod rack D d; and as the pillon is
Jeath.ered fo tight, as to 6t the bar,,1 exaélly, r can
get between the piflon and barre!; and therefore, all the
. ir abo.e dio the barrel is liCted up towords B, aod a .acu–
um ¡, made in the barrel (rom t to h; upon which, .parl of
the air in the reeeiver M (fig. 8.) by its Cpring, rufhes througb
Ihe hole i, in the braCs pl. t< LL, along the pipe CCC (whieh
communieate. with both barrel. by the hollow trunk lHK
( I;g 9) aod, pufhing up the valve 6, enters ioto . he vaeaot
place 6, of th. barre! BK. For, where_e\'er t~e refiflanee
or preffure is taken off, the air will run to that place, ir it
can fi nd a pacrage.-Th.o, al the haodle F will be turned
forw",d, rhe piflon d, will,bedeprecr<d io the barre!: and, as
Ihe .ir whic 1 had gOt iota the barrel eanoot be pufhed baek
Ihrough the valve 6, it will aCeend through a hole in the pi–
llon, and through a valve at d; and be hindered by
that valve (rom returDlng ioto fhe barre), wheo lhe pitlon is
again raircd . Al lhe neX1 ra¡Gng of the pifion, a v¡¡cuum is
_gain madc in me rame rnílnner as befare, between 6 and t';
upon which more of (he alr, which was Jefe in lhe: reccivcr
M . gets out thence by its fpring, and runs Ime. lhe ba rrel
BK, throu gh the • • Ive B. The C,me thiog is tObe under_
Rood wlth rl!gard tO the other barrel A', ano as the handle
P is lUrnC'd backwílfds and rorwards. it alternately ratl'es
and cteprdres (he pifl ons io their barreis, always raiGng one
whilll it dt:prea"es ,he olher. And as (here is a vacuum
made in eaeh barre! when lIS pifion is ra¡fed , every particle
of air in the receiver M pu(hes out another, by liS fpring
or elaflicí' y, through the hole: ; and pipe ce. ioto the bar·
rels, until at laft the airio the receiver comes to be fo Oluch
dilated , and its fprinit (1,) r,H weak~n ....d. that ir can no longer
Rtt thrl')u~h the vi\lves : and 'Ihen no more can be t.ken
out , H ~nce there is no fuch thing as m.tki ng a perfc::lt
vacuum in the recei\'er: (or the quantlly of ai r tfikeo out al
DOy one flrc:ke. \\ ill always be as the dc:nfilY thereof io lhe
I"cceivr'rl aod lhutfurc it is impcffible tO takc it aJl out, be.
VOL , llr. N° 89. 2
A T 1 e s. ~9r
cauCe, fuppvf:ng the reeeiver aod barrel. oC equal cap.city,
there wdl be al" .,ys .. ","eh leCt as was takeo OUt at Ihe Jan
IUro of Ihe hand:<.
There is a cock l bel,J\:I lhe FHlmp.p'ate, which being
turned leu the ?ir lOtO (he recelVcr again: and then the
receiver becomes loofe, aod mly be uken off the plate, The
barreis are 6xed tO rhe frame Ea by two Cerew_nuts ff,
which PI éfs down the top piece E upon the barreis; and
the hoJlow trunk H (io 6g. 9,) is eovered by a box, as CH
in 6g 8.
T here is a glaC. tube Imm",n npen al both end., aod a–
bout 34 ¡nches long; lhe upper tnd comrnuoicaling widl
lhe hole iD Ihe pump.plate, alld lhe lower eod Immtrred in
quiekfilver at n in the ve/fel N . To thi. tu~e i. 6tted a
wooden ruler ,'!1IJ, caBed the gQg~, whicn is divided ioto
incbes and pans of ao ¡nGh, (rom lhe bouom at n ( where
it is eveo with the furface of (be quickGlver) and contioued
up tO the top, a liule bdow /, to 30 or 3 I inehe~.
As Ihe air is pumped OUt of lhe receiver /11, it is Jikewife
pumped out of the rube Imn, beeauCe that tube opeo.
iOlo Ihe receiver througb Ihe pump. plale j and as lhe lube
is gradoally emptied of air, the qu,ekfilver in the vecrel N
is forced up into tbe tube by the precrure of the atmoCphere;
And if the reeei..r eould be perfeélly exh,ufled of air, the
quiekfilver would flaod as high in the tube as it does al that
time io the barometer : for it i. Cupported by <he fame power
or weight of the at moCphere io both_
T he qu.n,i,y of air exhaufled OUt of the recei:ver 00
turo of the haodle, is aJways proportion.ble tO the aCeent of
the quickG)ver on Ibat turo ; aod the quantlty of air re–
maining in the receiver, is proportionable 10 lhe defed of
the height of the quiekfilver iD the gage, (rom wh.t it is al
-that time in lhe barometer.
EXPERIMENTS W·ITH TorO AIR.PUMP,
1, 7 ojh('1JJ Ih, "jiflan« oflh, airo
l. THERE is a Jittle machioe, coofifiing of two mifls, ti
and 6, (i6id. 6g. 10.) ",hieh are of equal weights, inde–
pendeDt of e<tch other, aod turo equaJly free on Iheir axel
in the frame. Eaeh mili h•• four thio arms <>r fail. ñxed
ioto the axi.; thoCe of the mili a have their pl.nes at rig~t
.ngles to its axis, and thoCe of 6 have their pl anes parallel
to it. Therefore, as Ihe mili Q turos rouod incoromon air.,
it i. but litde refifled thereby . bee·,uCe itS C,ils CUt the air
witb their tbio edges : but the mili 6 i. m,ueh reGflcd, be–
caure .the broad fidts of 115 (ails move againn the air whell
it turo, rDund . In each axle IS a pin near the O1iddl~ of lhe
frame. which got's quite through the axle, and flands out
a litlle on each fide of il ; upon tbefe pio" the.1l.der ¿ m1y
be madc: 10 bt'ar. and (o hinder (he mdls from g'ling wheD
the lIroog Cpriog e u Cet 00 bend ag.inl! the oppofitc eod. of
the pins .
H .ving Cet , his maehioe upon the pump. plate LL (6g. 8.)
draw up the l]lder d tO ,he plns OD one fiete, and {~t lhe
fprlOg e ,H be; nd upon the oppofite ends of lhe pir.s ; th~n
pulh down the Oidor d. and ,he Ipring .élin~ equally l!tone
00 cach mili , WIII {e l theOl bOlh agolng wlth eq u.l1 forces
and vclocilles : bUI the mili Q \\'ill ruo much loogc:r thAn Ihe
mili 6, becauCe the air makcs mueh leC. ..fill altee ag.inl!
,he odges of iu Cails thao agaiol! the tides of the Cail.
of 6.
6 H t Dra",