262 



FKAGHENTS OF SCIENCE. 



unanimity, the gun-cotton detonated in free air wag 

 placed second in intensity. Though the same charge 

 was used throughout, the guns differed notably among 

 themselves, but none of them came up to the gun-cotton, 

 either with or without the reflector. A second series, 

 observed from a different distance on the same day, 

 confirmed to the letter the foregoing result. 



As a practical point, however, the comparative cost 

 of gun-cotton and gunpowder has to be taken into 

 account, though considerations of cost ought not to be 

 stretched too far in cases involving the safety of human 

 life. In the earlier experiments, where quantities of 

 equal price were pitted against each other, the results 

 were somewhat fluctuating. Indeed, the perfect mani- 

 pulation of the gun-cotton required some preliminary 

 discipline promptness, certainty, and effectiveness of 

 firing, augmenting as experience increased. As 1 Ib. of 

 gun-cotton costs as much as 3 Ibs. of gunpowder, these 

 quantities were compared together on the 22nd of Feb- 

 ruary. The guns employed to discharge the gunpowder 

 were a 12-lb. brass howitzer, a 24-lb. cast-iron howitzer, 

 and the long 18-pounder employed at the South Fore- 

 land. The result was, that the 24-lb. howitzer, firing 

 3 Ibs. of gunpowder, had a slight advantage over 1 Ib. 

 of gun-cotton detonated in the open ; while the 12-lb. 

 howitzer and the 18-pounder were both beaten by the 

 gun-cotton. On the 2nd of May, on the other hand, the 

 gun-cotton is reported as having been beaten by all 

 the guns. 



Meanwhile, the parabolic-muzzle gun, expressly 

 intended for fog-signalling, was pushed rapidly forward, 

 and on March 22 and 23, 1876, its power was tested at 

 Shoeburyness. Pitted against it were a 16-pounder, a 

 5^-inch howitzer, 1^ Ib. of gun-cotton detonated in the 

 focus of a reflector (see annexed figure), and 1J Ib. of 



