546 ' PHILOSOPHICAL TRANSACTIONS. [aNNO 1779- 



apt to fail. As this inflammable air is heavier than common air, it is clear that 

 the mouth of the air pistol should be kept upwards at the time of charging it ; 

 whereas it is better to invert the pistol when the ortiinary inflammable airs are 

 employed, which, being specifically lighter than common air, rise of themselves 

 in the pistol when its mouth is placed inverted on tlie orifice of the vessel which 

 contains them. 



It is true, that the squeezing the elastic gum bottle, when placed on the 

 pistol, forces some of the inflammable gas out of it, which is lost in the com- 

 mon air ; but notwithstanding this waste, the inflammable air which remains in 

 the pistol is sufficient to produce a loud report, which is all that is required. 

 Indeed, one single drop of the aether could be easily shaken out of the glass tube, 

 immediately into the pistol, without making use of the elastic gum bottle ; but 

 this drop, evaporating into elastic air, leaves behind it a good deal of moisture, 

 whether inherent in the aether itself, or attracted from the atmosphere. This 

 moisture, in the way I use to load the pistol, remains in the elastic gum bottle, 

 which is therefore always found moist when the experiment is repeated several 

 times. 



It was, indeed, known before this time, that aether and other volatile inflam- 

 mable liquors spread by evaporating inflammable effluvia through the surround- 

 ing air, especially when they are heated ; and that these effluvia have sometimes 

 by the imprudent approach of a candle taken fire, and conveyed the inflamma- 

 tion to the liquor itself: but I never heard that any body employed these liquors 

 instead of ordinary inflammable air in communicating to common air an explo- 

 sive quality, or in firing inflammable air pistols, before I communicated the ex- 

 periment to my friends. As it will, I think, appear very probable, by what will 

 be said hereafter, that little more than a pleasing amusement can be expected 

 from the force of any inflammable air ; the ready production of such inflamma 

 ble air always ready for use, when an explosion is intended to be produced, may 

 be of some importance to philosophers, whose time must be sparingly taken up. 

 Comparative view of the expanding force of explosive air and gunpowder. — 

 The force of gunpowder has been ascribed by Sir Isaac Newton, and all other 

 philosophers, to the sudden extrication of an amazing quantity of elastic perma- 

 nent aerial fluid within a narrow space incapable of containing it ; which quantity 

 ought to be attentively attended to, in order to estimate the comparative power of 

 the two substances. Benjamin Robins, whose work, entitled, New Principles 

 of Gunnery, passes in this country for a standard book, affirms, that gunpowder, 

 when fired, generates a permanent elastic fluid of 250 times the bulk of the 

 powder before it was fired. He found that common air, whicli is heated by the 

 contact of a red-hot iron, expands to 4 times its former bulk. Hence he con- 

 cludes;, that the elastic air, disengaged from gunpowder, must expand also to 

 4 times its dimension; and that it occupies about lOQO times the bulk of the 

 powder in the moment of inflammation. 



