DISCHARGING OF ORDNANCE. 507 



out myself counting the number of meshes which it 

 contained. 



The five following experiments are meant to re- 

 move any misconception on this part of the investi- 

 gation. I have confined my notices to two kinds of 

 gauze ; the one considerably coarser than the other. 

 A square inch of the coarser gauze contained 1296 

 meshes, being 36 wires in the length ; and the same 

 quantity of the finer gauze contained 4900 meshes 

 in the square, being 70 wires in the length. Now, 

 upon examining two of Sir Humphry Davy's lamps, 

 one for magnetic purposes with copper gauze, and 

 another for common work with iron gauze, I find, 

 that an inch of the gauze of the former confains 

 only 26 meshes in the length, and 676 in the 

 square ; and that the gauze of the latter contains 

 28 meshes in the length, and 784 in the square ; 

 shewing, that even the coarsest wire-cloth which I 

 have used, is finer than what is employed in the 

 safety lamp ; and that my results acquire additional 

 strength in proving, that the wire-gauze is not im- 

 pervious to the flame extricated by the explosion of 

 the fulminating powder. 



Experiment 13. — A tube, which could be sepa- 

 rated into six pieces of nearly the same length, was 

 screwed to the apparatus, making the distance from 

 the top (A) to the bottom, fully 23 inches. A 

 piece of the coarser wire-gauze already described, 

 was put upon the hole at the joining a, when the 

 fulminating powder was exploded at A, the flame 



