A 1 R 



A I R 



A over ihii hole of die pump plate, and as you exhauft'the 

 air, tlie bladder will be prcfled down and aiTiime within ih.; 

 glafs a concave figure, and at length it will break with aloud 

 report. If a piece of flat glafs be laid upon the top of this 

 receiver, and joined to it by a rim of wet leather, the pvcfl'ure 

 of the outward air will break the glafs, when the internal 

 air is cxhaufttd. 



5. Immerle the nee!; c ^ of the hollow glafs b<all e h {fg. 

 29.) in the water of liie phial a a ; place it on the plate of 

 the pump, and cover it and the hole of the plate with the 

 receiver A ; exiiauil this receiver, and the air will cfcape by 

 its fpring from the ball c li, through the neck d c, rife in 



. bubbles llirough the water, and pafs off into the external 

 all-. When it has done bubbling, turn the cock of the 

 pump, and the air that is admitted will by its preffure on 

 the iurface of the water foice it up in a jet into the ball <■ I, 

 and ahnoll fill it ; the ini^ll quantity of remaining air, which 

 occupied the Vvholeijall, and which is now reduced to a fmall 

 fpace of condeniation, preventing the water from filling the 

 whole cavity of the bail. This experiment may be varied 

 by fcrewing the end A of the brafs pipe A B F {Jig. 30.) 

 into the hole of the pump plate, and placing, bv means of 

 wet leather, upon the plate c ii d tall receiver G H clofe 

 at the top, exhauiling the receiver of its air and flopping 

 the pipe by the cock e ; when this is done remove the ap- 

 paratus from the pump, fet its end A in a bafon of water, 

 and open the pipe by turning the cock e ; and the pref- 

 fure of the air on the water will force it up through the pipe, 

 fo that it will afcend in a jet to the top of the receiver. 

 See FouxTAiv. 



6. Set the jar D (fy. 31.) containing quickfilver, near 

 the hole of the pump plate, and cover botli with the tall 

 open receiver A B. Into the plate C, placed upon the upper 

 end of this receiver, introduce the open glafs tube g /', im- 

 merfed at its lower extremity in the quickfilver of the jar D, 

 and fcrev.-edby a brafs top annexed to it at h to the fyringe 

 H, which is itfelf ferewed to the plate C. By the ring I 

 draw up the pifton of the fyringe, and thus exhaull the tube 

 of its air ; and the quickfilver in the bafon prcfTed by the 

 undilated air of the receiver A B will afcend in the tube. 

 That this afcent is owing to the preffure o^ the air, and not 

 to what fome have called fuftion, may b-. evinced by ex- 

 haufting the receiver of its air, which will caufe the quick- 

 filver to defcend into the jar, and by readmitting the air, 

 which will raife it again in the tube, although the piitou of 

 the fyringe be not moved. If the tube be about 32 or 33 

 inches high, the quickfilver will rife nearly as high in the 

 tube as it ftands at that time in the barometer. If the 

 fyringe has a fmall hole at m, and the pifton be drawn up 

 above that hole, the air will pal's through it into the fyringe 

 and tube, and the quickfilver will immediately fall down 

 into the jar. 



7. Place the jar A (y?f. 32.) with quickfilver in it on the 

 pump plate, cover it with the receiver B, and pulh the open 

 end of the glafs tube Jf through the collar of leathers in 

 the brafs neck C, almofl down to the quickfilver in the jar. 

 Exhauft the receiver B of its air, and the tube d e, which is 

 clofe at thetop_/', will at the fame time be exhauftcd. When 

 the receiver has been well exhauftcd, pufti the open end of 

 the tube ivto the quickfilver of the jar ; and though the 

 lube be exhauftcd of its air, the quickfilver will not rife in 

 it, becaiife there is no preffure on the furfaee of that in the 

 jar. But upon admitting the air into the receiver, the 

 quickfilver will immediately rife and (land as high as it did 

 In confequencc of the aCiJon of the fyringe in the preceding 

 cxperimcHt, 



Vot. I. 



Thcfc two laft experiments not only exhibit the Weight 

 and prefFure of the air, but they alfo Ihew that thefe are iii- 

 c.'cafed or diminilhed in proportion to the increafeor decreafe 

 of the air's depth. See Baromlter and ToRRictLLiAN 

 F.xpcnminl. 



S. Join the two brafs hemifphercs A and B together {fy. 

 36.) by the interpolition of a wel leather, v.lth a hole in tlic 

 middle of it ; then fcrew the end D into tlie plate ol the 

 pump, and turn tlie cock E of the pipe, C D, conununicating 

 with the hemifpheres ; and having exhaulled the air, turn 

 the cock fo as to Hop the pipe. Having removed it from 

 the pump, fcrew at the end D, the piece V h ; and two 

 ilrong men pulling at the handles g and h will lind it dilficull 

 to feparate the hemifpheres ; for if the diameter be four 

 inches, they will cohere together with a force ccjual to iSS 

 pounds, the area being equal to the fquare of the diamtler 

 multiplied by ,7854, and the predure on every fquare inch 

 being 15 pounds; ;. c. i6 x, 7SJ4 x 15 = l!)8,4i;(» 

 pounds. If they be fufpendcd by either of the rings 

 on the hook P of the receiver M {Jig. 3C.), and the re- 

 ceiver be exhaulled of its air, they will fepai-ate of Uiem« 

 felves. 



9. iSet the fquare phial A {Jig. 37.) upon the pump plate, 

 and cover it with the wire cage B ; then placing it under a 

 clofe receiver, exhauft the receiver and the phial which has a 

 fmall hole under a valve at L of their air ; and the air upon its 

 readmiffion into the receiver, being prevented from palfing 

 into the phi;J by the valve- b, will break it into a number of 

 pieces by its prefiure. Q^iiekfilver may be alfo forced into 

 wood, and made to pafa through it by the prefiure of the 

 air. 



II. Experiments for fliewing the elafticity or fpring of 

 the air. 



I. Place a bladder, containing a fmall quantity of air and 

 well tied up, under a receiver ; and when the receiver is ex- 

 hauftcd, the air will expand and fill the bladder fo that it 

 Villi appear as if it were blown with common air. Upon 

 letting in the air, the bladder prefied by it will be re- 

 duced to its original flaccid ftate. This bladder put into a 

 box under a weight of 20 or 30 pounds, and covered with a 

 receiver, will, upon the exhauftion of the receiver, raife the 

 weight by means of the fpring of the internal air. 



3. Take the glafs ball {Jig. 29.) which was filled with 

 water, a fmall bubble of air at the top of it excepted, and 

 having placed it with its neck downward into the empty jar 

 a a, and covered it with a clofe receiver, exhauft the receiver 

 of its air, and the air-bubble will expand itfelf, and by its 

 elaflic force protrude the water out of the ball into the jar. 

 Or, fcrew the pipe A B {Jig. 30.) into the pump plate, and 

 place the tall receiver G H upon the plate c <!; exhaufl the 

 receiver, and then remove the apparatus and fcrew it into the 

 copper veffcl C C {Jig. 38.) half filled with water. Then 

 turning the the cock e {fig. 30.) and the air confined in this 

 vefl'el will by its fpring force the water through the pipe A 

 B, and caufe it to form a jet into the exhauftcd receiver, 

 equal to that which was produced by the preffure of the 

 air In a former experiment ; other circumtlances being 

 alike. 



3. Let the balls annexed to the heads of the hollow glafs 

 images {fig. 39.) contain watc- fufftcient to render them fpe- 

 cifieallv heavier than water. Place them under a receiver 

 and exhauft it ; and the air in the bulls will dilate, force part 

 of the water out, and relider the images lighter than water, 

 fo that they will afcend. On re-admitting the air, they will 

 defcend. Sm;ill apertures made in the feet of thefe images 

 will vary the experiment, and anfwer the fame pui-pofe. 



3 Q, 3. Animak 



