260 



FRAGMENTS OF SCIENCE. 



nary trials conducted at Woolwich on the 4th of June, 

 1875, the sound-producing powers of four different 

 kinds of powder were determined. In the order of the 

 size of their grains they bear the names respectively of 

 Fine-grain (F. Gr.), Large-grain (L. Gr.), Eifle Large- 

 grain (R. L. Gr.), and Pebble- powder (P.) (See annexed 

 figures.) The charge in each case amounted to 4^ Ibs. ; 



m 



* 



^ 



F.G. 



L.G. 



B. L. G. 



P. 



FIG. 7. 



four 24-lb. howitzers being employed to fire the respec- 

 tive charges. There were eleven observers, all of whom, 

 without a single dissentient, pronounced the sound of 

 the fine-grain powder loudest of all. In the opinion of 

 seven of the eleven the large-grain powder came next ; 

 seven also of the eleven placed the rifle large-grain third 

 on the list ; while they were again unanimous in pro- 

 nouncing the pebble-powder the worst s,ound-producer 

 These differences are entirely due to differences in the 

 rapidity of combustion. All who have witnessed the 

 performance of the 80-ton gun must have been sur- 

 prised at the mildness of its thunder. To avoid the 

 strain resulting from quick combustion, the powder 

 employed is composed of lumps far larger than those 

 of the pebble-powder above referred to. In the long 

 tube of the gun these lumps of solid matter gradually 

 resolve themselves into gas, which on issuing from the 

 muzzle imparts a kind of push to the air, instead of 



