MANUFACTURE, ETC., OF GUNPOWDER. 725 



enter the press-room, a kind of catch and trigger is attached to the 

 side of the block, and, as soon as the press-box has been forced up to 

 the required point, the catch is liberated by coming in contact with it, 

 and rings a bell in the pump-room. The pumps are then stopped, the 

 ram falls by its own weight, and the box is unloaded, the gunpowder 

 being taken out in large cakes the size of the metal plates, and as hard 

 as slate. It is in the pressing of the gunpowder that the most seri- 

 ous explosions occur, for, if by any chance the pressure becomes too 

 severe, and the powder explodes in the box, its force is much greater 

 than if it were ignited in the open air. Seven men were killed by an 

 explosion in the press-house at Waltham Abbey in 1843, and by a 

 similar accident on June 16, 1870, five were killed and seven injured. 



The question of the density given to gunpowder by pressing and 

 its effects is one which is only now being worked out. Formerly the 

 density of the powder was roughly ascertained by weighing a cubic 

 foot of it, and then its quality was tested by observing to what dis- 

 tance it would fire a shell from a mortar. The primitive methods are 

 now superseded by a testing apparatus, which gives scientifically 

 accurate results. The density is determined by reducing a small 

 quantity of the jjowder to dust in a mortar, and then placing it in a 

 glass globe provided with stopcocks, one of them connected w r ith an 

 air-pump, and the other with a tube dipping into a vessel of mercury. 

 On exhausting the air, closing the first cock and opening the second, 

 the mercury is forced into the globe, and completely fills it. It is then 

 weighed in a delicate balance, and, its weight when filled with mer- 

 cury only being known, it is easy to calculate the density of the gun- 

 powder. 



Its force is ascertained by observing the initial velocities which it 

 will give to a shot fired from a cannon. These velocities are 

 measured with Bashforth's Chronograph, as explained in a former 

 article in the Popular Science Review ; 1 and with the Noble Chrono- 

 scope, the invention of Captain A. Noble, of the Elswick Works, by 

 means of which we are enabled to ascertain what takes place in the 

 bore of the gun on the explosion of the charge, and what is the veloci- 

 ty of the shot, not only in the whole length of its course within the 

 gun, but also in each portion of that short distance, thus determining 

 the velocity within very small limits both of time and space, and this 

 with the most perfect accuracy. 



It is difficult to describe the chronoscope without a diagram, but 

 it is easy to indicate the general principles of its action in a few words, 

 and this will be sufficient for our purpose. A gun having been selected 

 for the experiment, six or eight holes are drilled in one side of it, pene- 

 trating to the bore, at intervals along its length from the seat of the 

 shot to the muzzle. Through each of these holes an insulated wire 



1 " On the Striking Velocity of Shot." By W. Royston Pigott, M. D., P. S. R., Janu- 

 ary, 1871. 



