1874.] 



on Fired Gunpowder. 



409 



The gunpowder operated upon in the experiments includes five kinds, 

 viz. pebble powder, rifle large-grain (cannon) powder, fine-grain powder, 

 and rifle tine-grain powder (all of Walthara- Abbey manufacture), and also 

 a spherical pellet powder of Spanish manufacture, specially selected for 

 experiment as presenting considerable difference in composition from 

 the English powders. The composition of the powders is shown in the 

 following Table : 



TABLE I. 



Results of Analysis of Gunpowders employed. 



The quantities of gunpowder exploded in the several operations ranged 

 from 750 grammes to 100 grammes. The following is a description of 

 the apparatus in which the charges were exploded : 



The apparatus consisted of a mild steel vessel, of great strength, care- 

 fully tempered in oil, in the chamber of which the charge to be exploded 

 was placed. The main orifice of the chamber was closed by a screwed 

 plug, called the firing-plug, fitted and ground into its place with great 

 exactness. 



In the firing-plug itself was a conical hole, stopped by a plug, also 

 ground into its place with great accuracy, and, for purposes of insulation, 

 covered with the finest tissue-paper. Two wires (one in the insulated 

 cone, the other in the plug) were inserted, and joined by a very fine 

 platinum wire passing through a small glass tube filled with mea'ed 

 powder. By completing connexion with a Daniell's battery, the charge 

 could be fired. 



There were two other apertures in the chamber one communicating 

 with the arrangement for letting the gases escape, the other containing 

 the crusher-apparatus for determining the tension at the moment of 

 explosion. 



The pressures actually observed with the apparatus just described 



2i2 



