A I R 



A I R 



To the air-pump belongs a large apparatus of other vefTcls, 

 accommodatal to various kinds of experiments. 



Befidcs the efiecls, and the phenomena of the air-pump, 

 recounted under the articles Vacuum, Air, &c. we may 

 add fon-.e others ; whicli, related at large, make the fub- 

 ft.mcc of Mr. Boyle's Phyfieo-Mech. Exper. — As, that the 

 flame of a candle in viiruo ulually goes out in a minute, 

 though it fomctlmes lails two, but the uiek thereof con- 

 tinues ignited after ; and even emits a fmoke, which alcends 

 upwards. — That a kindlid charcoal is totally extinguilhed 

 in about five mimites, though in open air it remain ahve 

 half an hour ; that it goes out by degrees, beginning from 

 the top and the outfides. — That red-hot iron is not affected 

 by the abfe;icc of the air; and yet that fulphnr or gun- 

 powder will not be hghted thereby, but only fufcd. — That a 

 match, after lying fcemingly extinct in viinio a long time, 

 revives again upor the re-admiffion of the air. — That a flint 

 and fteel ftrike fparks of lire as copioufly in vacuo as out of 

 it ; and that the fparks move in all direClions, upwards, 

 downwaids, &c. here as in the air. — That magnets and 

 magnetic needles, are the fame iti -vacuo as in air. — That 

 fmoke in an exhaufted receiver, the luminary being extindl, 

 j^radually fettles to the bottom in a darkifli body, leaving 

 the upper part clear and tranfparent ; and that inclining the 

 Ncffel lometimes on one fide, and fometimes another, the 

 fume keeps its furface horizontal, after the nature of other 

 fluids — That the fyphon does not run in •vacuo. — That water 

 freezes in -vacuo. — That heat may be produced by attrition 

 in the exhauiled receiver. — That camphor will not take fire 

 in -vacuo ; and that gun-powder, though fome grains of a 

 heap be kindled by a burning-glafs in vacuo, will not give 

 fire to the contiguous grains. — That glow-worms lofe their 

 hght in proportion as the air is exhaufted, and at length 

 tecomc totally cbfcure ; but upon the re-admiflion of air, 

 prcfently recover it all. — That eledricity appears like the 

 Aurora borealis. — That vipers aud frogs fwell much in 

 vacuo, but will live an hour and half, or two hours ; and 

 though feemingly quite dead in that time, come to life again 

 after being fome hours in the air. — That fnails furvive ten 

 hours ; and efts or flow-worms, two or three days ; leeches 

 five or fix — That fifiies will rife up to the top of water, 

 placed under an exhaufted receiver, beeaufe the air-bladder is 

 expanded, and they are thus made fpecifically fighter than 

 water ; but if the bladder breaks, they fink down to the 

 bottom and rife no more. — That animals who five in water 

 viU not die by exhaiifting the air out of the receiver, unlefs 

 they are kept for a confiderable time in vacuo. — That 

 oyfters will remain alive in vacuo 24 hours without harm — 

 That the hea.t of an eel taken out of the body, continues 

 %o beat in vacuo, more nimbly than in air ; and this for a 



good part of an hour That warm blood, milk, gall, &c. 



undergo a confiderable intumefcence and ebulhtion in vacuo. 

 — That a moufe, or other animal, may be brought, by de- 

 grees, to furvive longer in rarefied air, than naturally it 

 does. — That air may retain its ufual prefTure, after it is be- 

 come unfit for refpiration. — And that filk-worms' eggs will 

 hatch in vacuo. 



Befides the above-mentioned phenomena, many others are 

 recited by different writers on this fubjeft, and they may be 

 found in the Philofophical Tranfaftion of various Academies 

 and Societies, and in the works of Torricelli, Pafcal, Mer- 

 fenne, Guericke, Schottus, Boyle, Hooke, Haukfbee, 

 Duhamel, Mariotte, Hales, Mulchenbroek, Gravefande, 

 Defaguhers, Franklin, Cotes, HeKham, Martin, Fergufon, 

 Adams, &c. &c. We fhall fubjoin for the exercife and 

 amufement of our readers fome farther experiments, arranged 

 under diflinft heads. For experiments that require peculiar 



accuracy, the receiver fhould not be placed upon leather* 

 either oiled or foaked in water ; but the plate of the pump 

 fliould be made very dry, and the infide of the receiver 

 fiinuld be dried and rubbed with a wami cloth. The re- 

 ceiver may then be let upon the plate, and hog's lard, cither 

 alone or mixed with oil, be froeared round its outward edge. 

 After performing any experiments, the pump (hould be 

 cleared of any vapour tliat has been geiieialcd, by exhauft- 

 ing a large receiver to ad great a degree as pofiible ; and the 

 vapour that remained in the banel and pipes will be diffufed 

 through the receiver ; and if this be large, one exhauftioii 

 will be iuflicient for clearing the pump. With fmall re- 

 ceivers the operr.lion fliould be repeated two or three times. 

 In fome of the beft pumps, the plate and edges of the re- 

 ceiver aie grc','nd lo accurately as not to require any 

 leathers ; but as the plate is liable to befcratched by fetting 

 the receivers upon it, hog's lard or tallow ipread ujKm their 

 edges will be ufeful. This will prevent the edges from da- 

 maging the plate, and will not admit any vapour. When 

 leathers are ufed for connefting the receiver with a pump 

 plate and for making the junftion air-tight, they are prc- 

 vioufly foaked in water, oil, or a mixture of melted bees* 

 wax and hog's lard. Vi^hen experiments are performed that 

 require the ufe of mercury, a fmall pipe fhould be fcrewcd 

 into the hole of the pump plate, in oiiler to prevent any of 

 it, that may be accident dly fpilt, from pafTing into the air- 

 pipe and barrels ; which would loofen the folder and conode 

 the brafs. 



I. Experiments for fhewing the weight and prefTure of 

 the air. 



1. Exhauft of its air acopper ball.fuch as C (P/a/c- V. Pneu- 

 matics, Jig. 26.) the neck of which is furnilhcd with a ftop-cock 

 and a fciew by means of which it may be fixed to the plate of 

 an air-pump ; fufpend it, when exhauiled, on the end B of 

 one arm of a bHlarice, A B, and lay upon it the fmall weight 

 p, which muft be counterpoifed by a weight P in the op- 

 pofite fcale of the balance. Turn the cock of the ball, and 

 the air will rufh in and render it fo much heavier, that the 

 weight p muft be removed in order to reftore the equilibrium. 

 If the ball holds a gallon, it will thus be found that a gallon 

 of air weighs about the fixth part of an ounce. See 

 Weight of the Air. 



2. Place the fmall receiver O {Jig. 35'.) over the hole of 

 the pump plate, and upon ex'iauiiing the air, the receiver 

 will be fixed down to the plate by the prefTure on its outfide ; 

 and this prefTure will be equal to as many times 15 pounds 

 as there are fquare inches in that part of the plate, which 

 the receiver covers. By turning the cock of the pump and 

 readmitting the air, the receiver will become loofe. In 

 order to prove tbat the receiver O is held down by the 

 prefTure of the air, fufpend it on the hook of the wire P P 

 pafTing through the collar of leathers at the top of the re- 

 ceiver M, by which it is covered, and thus let it down on 

 the plate of the pump ; and when the air is exhaufted from 

 both receivers, the large receiver M will be fixed to the plate 

 by the prefTure of the external air ; but the fmall one O 

 will be loofe and may be eafily removed ; on letting in the 

 air, the lefTer O will be fixed down upon the plate and the 

 other will be rcleafed. 



3. Place a fmall brafs or glafs vefTel A B (Jig. 27.) which 

 is open at both ends over the hole of the pump plate, and 

 cover the top of it with the hand ; which, when the air is 

 exhaufted, will be prcfTed down by the weight of the ex- 

 ternal air, fo that it cannot be releafed without difficulty till 

 the air is readmitted. 



4. Tie a piece of wet bladder, as b (f.g, 28.) over the 

 open top of the glals A ; when it is dry, fei the open end 



