258 APPENDIX B. 



duced very nearly the same effect as if the elastic, 

 fluid had been a mixture of air and combustible 

 gas, of air and carburetted hydrogen gas,, for ex- 

 ample. There was a sort of explosion, and a sud- 

 den dilatation of the elastic fluid & dilatation that 

 was utilized by making it act upon the piston. 

 The latter may have a motion of any amplitude 

 whatever, and the motive power is thus realized. 

 The air is next renewed, and the operation re- 

 peated. 



This machine, very ingenious and interesting, 

 especially on account of the novelty of its princi- 

 ple, fails in an essential point. The material used 

 as a combustible (it was the dust of Lycopodium, 

 used to produce flame in our theatres) was so ex- 

 pensive, that all the advantage was lost through 

 that cause; and unfortunately it was difficult to 

 employ a combustible of moderate price, since a 

 very finely powdered substance was required which 

 would burn quickly, spread rapidly, and leave little 

 or no ash. 



Instead of working as did MM. Niepce, it would 

 seem to us preferable to compress the air by means 

 of pumps, to make it traverse a perfectly closed 

 furnace into which the combustible had been in- 

 troduced in small portions by a mechanism easy of 

 conception, to make it develop its action in a cylin- 



