132 On the instantaneojii Producliofi of Fire, isfc. 



with this instiument, I am induced to htln-ve, that the 

 accensioii oF the combustible bodies which is effected in the 

 manner stated, is not simply owing to the mere instantaneous 

 condensation of the air which takes place in the syringe, and 

 subsequent liberation of caloric, as stated by the continental 

 philosophers: but tliat, on the contrary, it appears to be ow- 

 ing to the intense and rapid mechanical motion, vibration, 

 or friction, produced in the particles of the body, placed in 

 the chamber of the instrument against each other by the 

 rapid current produced. For it was found that only such 

 bodies as are exceedingly porous, or arc made up of a multi- 

 tude of minute fibres, could be set on fire by means of this 

 instrument ; and that the accension of compact combustible- 

 substances, or bodies of a different texture, when attempted, 

 always failed. Hence phosphorus, phosphuret of sulphur, 

 camphor, ether, naphtha, fidminating gold, fulminating 

 mercurv, and other infl:n"nmable substances, which so readily 

 take fire, cannot be inflamed, nor can the thinnest piece of 

 foil, made of the fusible alloy which liquefies in boiling wa- 

 ter, be melted by the current of compressed air thus effected. 

 The case is otherwise when a porous or fibrous inflammable 

 body is suddenly struck upon ; a piece of common tinder, 

 a piece of amadou, very dry tow, rolled up in a coil, com- 

 mon touch wood, and the scrapings of dry paper, or linen 

 rag, are instantly inflamed by a stream of condensed air. 

 Hence it appears, that the accension of these bodies is not 

 solely owing to the mere disengagement of caloric, of which 

 the air is deprived when its volume is suddenly contracted. 

 Biot has, indeed, announced in the Magas, Enajclop. for 

 April J 805, that The effect of a very instantaneous com- 

 pression of oxygen and hydrogen gases might be substituted 

 for the electric sp.iik, in the performance of the famous ex- 

 periment elucidating the production of water. He states, 

 that having introduced into an air gun a mixture of the two 

 gases, and having given a sudden stroke to the piston, a vivid 

 light accompanied with a violent detonation took place, in- 

 dicating the combination of the bases of the two gases. This 

 important experiment, which no doubt will be repeated by 

 others, stands, nevertheless, unconected with what has been 



advanced. 



