.1821.] regarding the Experiments upon Flame. 207 



inch. Now upon examining two of the lamps recommended by 

 Sir H. Davy, the one with copper gauze, and the other with iron 

 gauze, 1 found the former had only 676 meshes in the square 

 inch, and the latter 784 meshes in the same space. 



Experiment 13. — A tube which could be separated into six 

 pieces of nearly the same length, was screwed to the apparatus 

 (Plate III, p. 89), making the distance from the top. A, to the 

 Ibottom fully 23 inches. A piece of the coarser wire gauze, 

 already described, was put upon the hole at the joining, «, when 

 the fulminating powder was exploded at A, the flame passed 

 through the gauze, and appeared at the bottom of the tube. The 

 same kind of wire gauze was next placed at a and b at the same 

 time, and then at «, b, and c, and the flame passed through all 

 the pieces. This effect was also obtained when similar pieces of 

 wire gauze were put at all the five joinings of the tube at once. 

 In this last result, the first piece of wire gauze was 44- inches 

 from the top, A ; the second, 8^; the third, 12 ; the fourth, 16; 

 and the fifth, 20 ; and the flame appeared at the bottom, after a 

 passage of nearly 23-i inches, through five pieces of the wire 

 gauze. 



Experiment 14. — As I could not get the flame to pass through 

 the whole of the tube, when I increased the joinings beyond 23i 

 inches, it was impossible to try an additional number of pieces 

 of wire gauze, by adding them in the same way. I, therefore, 

 increased the number by putting more than one at the same 

 joining. I found, upon repeated trials in this way, using the 

 tube 15 inches long (as represented on the plate, p. 89, fig. 1), 

 that the flame could pass through three, six, nine, and twelve 

 pieces at once : there being placed one, two, three, and four 

 pieces at each of the joinings, a, b, and c. 



Experiment 15. — Although, by the two last experiments, it was 

 proved that the flame could pass through the coarser wire gauze 

 when increased even to 12 pieces at once, yet it did not follow 

 that it was not thereby altered somewhat in its nature A pro- 

 bable change was, that it might become inert with regard to 

 inflammables, as takes place in the different safety lamps, and 

 particularly that of Sir H. Davy. Several experiments were 

 tried to ascertain if this suggestion were correct ; first, the wire 

 gauze was put at a ; then at a and b ; and lastly, at «, b, and c ; 

 placing at the same time, during each trial, a quantity of gun- 

 powder in a piece of flannel at the bottom of the tube ; and in all 

 of these I found the gunpowder to be inflamed, and the wire 

 gauze not to be in the least injured. 



Experiment 16. — I next tried the result of firing the fulminat- 

 ing powder, with the finest wire gauze placed first at a, then at 

 a and ^, and then at «, b^ and c, and found that the flame still 

 appeared at the bottom, B ; showing that the gauze, although 

 much finer than that used in Sir H. Davy's safety lamp, was not 

 impervious to this flame. In some of the experiments I found a 



