common end of this tube was fixed a brafs barrel, like that of a piftol into this barrel a brafs bullet was put loofe, fo that the barrel was placed a little above the level, to prevent the bullet rolling out. The barrel was directed to a board of oak at eight or ten feet distance. A proper quantity of common and inflammable air (produced in the manner above mentioned) being drawn into the glafs tube by means of the pifton, it was fired by directing an electrical explosion through it. The explofion was very loud: the ball hit the board with fuch a force that it made a ftrong impreffion in it, and recoiled with a confiderable force, fo as to hit the wall behind us, and to put us in fome danger of being hurt by its rebounding force. The fame gentlemen told me, that this inflammable air had in fome refpects the advantage over the inflammable airs extracted from metals by the vitriolic or marine acid, and that extracted from mud or marshes; because this air being heavier than either of these airs, and even than common air, is not fo easily lost out of an open veffel; and, that when it efcapes into the open air, it agreeably perfumes the room with the fmell of Spiritus vitrioli dulcis or æther; whereas the other inflammable 'airs, which from their lefs fpecific gravity escape easily into the common air, yield an offenfive, difagreeable ftench. Mr. Æneae, having examined the fpecific gravities of the different inflammable airs compared with common air, favoured me with the following refult of his inquiries: A veffel, which contained the weight of 128 grains of common air, contained 25 grains of inflammable air extracted from iron by vitriolic acid, and 92 grains of inflammable air extracted from mud or marshes, and 150 grains of that extracted from oil of vitriol and fpirit of wine. I was much pleafed with the above-mentioned experiment, and immediately thought that the operation of extracting this inflammable air or vapour could be difpenfed with by employing vitriolic ather, which in reality is contained in the vapour expelled by heat from oil of vitriol and spirit of wine, which vapour, condensed in the procefs of diftillation, yields æther. The first attempts I made proved unfuccefsful; however, the reafons why I did not fucceed in the beginning I found afterwards to be, either that I employed too great a quantity of æther, or that the air or vapour of the æther was not thoroughly incorporated with the other air; for the fame number of drops of æther poured into the air pistol, which would not produce an explosion when the piftol was not fhaken, made a very loud one when it was forcibly agitated. The fureft method of fucceeding I find to be the following: I dip a fmall glafs tube, open on both fides, and the bore of which is one twelfth of an inch in diameter, into a phial containing æther, and when two or three drops of the liquid have entered the tube I apply my finger to the upper end of it, to keep the liquor fufpended. I take the tube out of the phial, and thruft it immediately into a fmall caoutchock, or elaftic gum bottle: this being done, I withdraw my finger from the tube, and take it out of the caoutchouck; thus the little quantity of æther, fufpended in the end of the tube, is dropped into the caoutchouck, the neck of which is to be immediately inverted into the orifice of the air pistol, and, after giving it a gentle fqueeze, withdrawn out of it: after which, a bullet or a cork is to be thruft into the mouth of the piftol, when it is ready for firing. This whole operation may be performed in the fpace of five or fix feconds. The confiderable force of explofion, and the loud report of the ordinary inflammable airs, induced Mr. Volta, of Como, to believe, that these airs might, perhaps, become a fubftitute to gunpowder. If this expectation had been well founded, the greatest defideratum would, I think, have been to find out a way to produce fuch air at any time without trouble, and to carry it about in as little compafs as poffible: which two conditions I fhould have pretty nearly fulfilled, as all the inflammable air requifite for the explofion of the piftols contrived by Mr. Volta is contained in the bulk of one fingle drop of ather; which drop, poured in the piftol itfelf, is full fufficient to produce a very powerful explofion. I found that æther, in which as much urinous phofphorus is diffolved as will make it luminous in the dark, when fome drops are poured upon water; is very brifk in taking fire, when employed for an inflammable air pistol; but that the experiment, when repeated, will be apt to fail, because the phosphoric acid which remains in the pistol, and by its nature at VOL. XXIII. tracts the humidity of the atmofphere, will foon fill the inside of the pistol with a coat of moisture, and prevent the electrical spark from kindling the inflammable air. It appeared, that a little camphire diffolved in æther increases its explofive force, and makes it lefs apt to fail. As this inflammable air is heavier than common air, it is clear, that the mouth of the air piftol fhould be kept upwards at the time of charging it; whereas it is better to invert the piftol when the ordinary inflammable airs are employed, which, being fpecifically lighter than common air, rife of themfelves in the piftol when its mouth is placed inverted upon the orifice of the veffel which contains them. It is true, that the fqueezing the elaftic gum bottle, when placed upon the piftol, forces fome of the inflammable gafs out of it, which is loft in the common air; but notwithstanding this wafte, the inflammable air which remains in the piftol is fufficient to produce a loud report, which is all that is required. Indeed, one fingle drop of the æther could be easily fhaken out of the glafs tube immediately into the piftol, without making ufe of the elaftic gum bottle; but this drop, evaporating into elaflic air, leaves behind it a good deal of moiure, whether inherent in the ether itself, or attracted from the atmosphere. This moisture, in the way I ufe to load the pistol, remains in the elaftic gum bottle, which is therefore always found moist when the experiment is 1epeated feveral times. It was, indeed, known before this time, that æther and other I vola volatile inflammable liquors spread, by evaporating, inflammable effluvia thro' the furrounding air, efpecially when they are heated; and that these effluvia have fometimes by the imprudent approach of a candle taken fire, and conveyed the inflammation to the liquor itfelf: but I never heard that any body employed thefe liquors inftead of ordinary inflammable air in communicating to common air an explofive quality, or in firing inflammable air pistols, before I communicated the experiment to my friends. Doctor Ingenhoufz next gives a comparative view of the expanding force of this air and of gunpowder, together with fome confiderations on the nature of the latter fubftance. In the appendix, he has given the following account of fome farther experiments on the fame fubject: In the foregoing paper I attempted to give a comparative view of the explosive force of gunpowder and inflammable explofive air, which latter I had found to be fo far fhort of the explofive force of gunpowder as not to conceive any well grounded hope that it could ever become a fubftitute to this ingredient. At that time I had not yet tried the effect of very pure dephlogifticated air combined with that inflammable air, into which I had found that vitriolic æther is chang-, ed in an inftant. I must acknowledge, that I had but fmall expectations from the force of these two airs combined; for as I had always obferved, that æther air combined with common air is lefs brifk in taking fire, and lefs powerful in exploding, than inflammable air extracted from the vitriolic or marine acid, I thought that the fame æther air combined with very pure dephlogifticated air would alfo be lefs powerful than common inflammable air from metals. But how far experience contradicted this theoretical analogy will be feen in the following lines. Abbé Fontana was fo good as to affift me in this purfuit. Having produced a good quantity of pure dephlogifticated air from red precipitate by heat, we first filled a ftrong two-ounce phial (the orifice of which was fo wide that it could scarce be covered with the thumb, fo that the bottle was almost cylindrical) with this air, in the ufual manner, by filling it first with water, inverting it, and letting the air rife in it; which being done, we dropped one drop of æther (in which a fmall quantity of camphire was diffolved) into it, and shut it immediately with the thumb. After having given it fome concuffions, the orifice was applied to the flame of a candle, by withdrawing the thumb when the orifice was clofe to the flame: the air inftantly took fire, and exploded with fuch a ftrong report, that, if the phial had not been very ftout, it would most probably have been shattered into pieces, notwithstanding its wide orifice. We repeated the fame experiment with the fame fuccefs. I was the more aftonifhed at the uncommon loud report (confidering the wide orifice of the phial), becaufe, having often tried æther air in the fame way with common air, I never found it explode with any confiderable degree of force; and therefore I found it neceffary, in order to procure a loud report, to to kindle it by an electrical fpark directed through the piftol, when its orifice was fhut up by a cork, the refiftance of which was the chief caufe of the report. This wonderful effect in an open veffel could not fail of giving me a good expectation of a very powerful effect, if this compound air was fhut up in an air piftol by a cork fqueezed into its orifice. As it had been now kindled twice by the flame of a candle, I wanted to kindle it by the fame means in an air piftol; for this purpose we drilled a small hole in the fide of the piftol, which was made of tin, and contained about nine cubic inches of space. We filled it with dephlogisticated air in the fame manner as we had filled the phial by means of water; and after having poured into it one drop of æther by means of a glafs tube (in the manner above defcribed), we fhut the ori fice by thrusting a cork into it, and kept a finger applied to the touch-hole which was drilled in the fide of the piftol. To avoid accidents if the pistol fhould burft, we thought it prudent to fqueeze the cork very gently into the orifice, fo that the refiftance fhould be very moderate. Abbé Fontana wrapped a towel round the piftol for fecurity's fake, leaving only the touch-hole uncovered; which being brought near the flame of a wax taper, the air inftantly took fire, and exploded with fuch a ftrong report, that his hearing, as well as mine, was much hurt by it. The cork, which was a very found one, flew to pieces against the wall; and the Abbé felt fuch a confiderable fhock in his hands, that he did not think it fafe to re peat the experiment, unless a ftronger piftol could be procured. Encouraged by fuch uncommon and unexpected effects, I went immediately to Mr. Nairne to enquire, whether he ftill had in his poffeffion a ftrong brafs air piftol, which he had made laft fummer according my direction? I was lucky enough to find it nothing was to be done to it but to drill a touch-hole in the left fide of it, in order to kindle it by a flame if required. This touch-hole was to be fhut up by a brass male screw fitted exactly to it, when the pistol was intended to be fired by an electrical fpark. The air box of this pistol was a cylinder four inches long and two inches in diameter. The fore part of the air box, to which the piftol barrel fitted to receive a leaden ball or a cork was fixed, had a broad fhoulder, which was fastened to the body of the air box by fix ftrong brafs fcrews, which never had been loofened by former explosions. A leaden bullet, wrapped up in leather, was forcibly rammed into the piftol barrel as far as the fcrew, which joins the barrel with the air box. The pistol was filled with pure dephlogisticated air (which was drawn-in by the pifton from an elaftic gum bottle), and one drop of æther being poured into it, the air within was kindled by an electrical spark directed through it. The air took fire: the explosion was as loud as that of a common mufket, and the force fo great, that the whole fore part of the air box with the piftol barrel flew off, all the fix fcrews were broke, and the strong and tough metal of which they were I 2 made made was rent. Three ftrong brafs fcrews, by which the bottom of the air box was fixed to the wooden handle, were loofened, and the whole frame of the piftol was out of order. The fubftance of the air barrel, where it was tore, was of the thickness of about a half crown piece. Being now convinced, that tho' inflammable air from metals with dephlogisticated or common air, is far inferior to the force of gunpowder, the explofive force of the compound of dephlogifticated and æther air approaches it much nearer, I thought it worth while to fit the piftol up in fuch a manner as to be out of all danger of bursting. For this purpofe I defired Mr. Nairne to adapt, and folder to the fore part of the air box, a hollow cone of brass, the extremity of which fhould terminate in the gun barrel. As the pifton could not reach to the extremity of this conical hollow (which confequently must be always filled with common air), I defired him to fix to the pifton an ivory cone, through which the two wires would pass to meet one another at the furface of the cone, leaving an interftice between them of about one line, through which the electrical park fhould leap and fet fire to the air. This ivory cone fhutting up exactly the whole cavity of the air box, no air could come into it but what was drawn in by the piston. The cone, inftead of ivory, may be made of folid glafs, which is a' better non-conductor than ivory. The canals in the ivory, through which the two wires pafs, may be made wide enough to contain a glafs tube, through which the wires pals; or to be filled with a non-conducting cement, as fealing-wax, for the fame purpose. The cone may even be made of brafs, provided two glass tubes are lodged in it, to give a paffage to the two wires. I kindle this pistol fometimes by putting in the touch-hole a little bit of a cotton thread foaked in moist gunpowder and dried afterwards; or a bit of thofe paper matches which the Chinese put into thofe little fquibs, which go by the name of India crackers. I fometimes kindle it by holding the flame of a candle or a burning paper to the touch-hole. In this cafe it is to be observed, that the touch-hole must be kept upwards, if the pistol is loaded with inflammable air from metals, because this air being lighter than common air, will rife out of the hole and meet the flame. The contrary must be done when æther air is employed, it being heavier than common air, and thus difpofed to defcend and fall upon the flame kept under it. To fill this piftol with any air, I commonly firft fill an elaftic gum bottle with it, the orifice of which is juft big enough to receive that part of the gun barrel which is fixed to the air box: thus, by fqueezing between my feet the elastic gum bottle, I draw in at the fame time the air by drawing up the piston. A bladder is allo very fit for this purpose, and has the advantage above an elaftic gum bottle in not requiring to be squeezed to draw the air out of it. Inflammable air from metals will rife in the piflol of itself, when |