3X6 



APPARATUS FOlt 



have produced the effect. In all these cases I was 

 careful to make the powder cover the whole surface 

 of the piece of flannel upon which it was poured. 

 This variety of effect seems to take place from some 

 accidental circumstances, which have as yet escaped 

 my notice. At some times I have apparently suc- 

 ceeded best when I used gunpowder, the grains of 

 which were large, and at other times again the 

 small-grained gunpowder was most uniform. 



The principal cause we may adduce for the pow- 

 der remaining uninflamed, under the above circum-f 

 stances, is the rapid motion of the flame. We are 

 entitled to draw this conclusion from the pheno- 

 mena which occurred in the 1st, 8th, and 10th expe- 

 riments ; in these we found that the flame did not 

 act upon the substances through which it passed, 

 when the resistance was feeble. But in the 9th and 

 10th experiments, when the resistance to which it 

 was opposed was increased, then its effect upon the 

 substances was more apparent. The same change 

 of ^effect seems also to take place with regard to 

 the gunpowder ; when the resistance is increased, 

 the powder is always inflamed, and the apparent 

 inertness only takes place when the motion of the 

 flame is left almost wholly free. The failure of 

 effect alluded to in several of the trials in the 24th 

 experiment, may have occurred from the flannel ha- 

 ving been too thick and compact, or from too large a 

 body of flame having passed down the tube at one 

 discharge. 



