506 



APPARATUS FOR 



to 23 i inches, and then it appeared very feeble, and 

 of a pale blue colour. 



Experiment 12. — The next circumstance which 

 seemed to claim inquiry, was the distance at which 

 the flame could explode the gunpowder. When 

 the gunpowder was put immediately in contact 

 with the lower aperture of a tube 23 \ inches long, 

 it was fired ; but when a piece of flannel interven- 

 ed it was not acted upon. Thus it appeared, that 

 although the flame, at 23 inches distance from the 

 source of its production, could inflame a quantity 

 of powder, yet it had not force enough to pierce 

 even one piece of flannel. The tube was now gra- 

 dually shortened, and trials made at each change, 

 till it was reduced to between 19 and 20 inches, 

 when it fired the gunpowder through the flan- 

 nel. 



I have repeated more extensively the experi- 

 ments with wire-gauze, which I noticed at a former 

 meeting ; and although it often happens that a 

 part of the finest kind is forced away or rent asun- 

 der by the flame, I find I was mistaken in my last 

 paper, when I imagined that the flame could not 

 pass through without injuring the texture of the 

 gauze. 



The first trials with wire-gauze were made very 

 hurridly; but the chief mistake arose from using 

 the gauze upon the assurance of the manufacturer, 

 that it was the same as used in the safety lamp, with- 



