260 FRAGMENTS OF SCIE^ T CE. 



pletely verified by experiment. In a series of prelimi- 

 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. G.), Large-grain (L. G.), Eifle Large- 

 grain (E. L. G.), and Pebble-powder (P.). (See an- 

 nexed figures.) The charge in each case amounted to 



FIG. 7. 



F. G. L. G. R. L. G. 



4 Ibs.; four 24-lb. howitzers being employed to fire the 

 respective 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 pronouncing the pebble-powder the 

 worst sound-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 surprised at the mildness of its thun- 

 der. To avoid the strain resulting from quick combus- 

 tion, 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 



