the Combustion of Gun- cotton and Gunpowder. 269 



that in this way it is possible not only to burn the gun-cotton 

 under different resistances, but also to obtain the resultant gases 

 free from atmospheric air. 



The resistance of the explosion-vessels must be so chosen that 

 the gas in the mortar, after explosion, has an excess of pressure of 

 half an atmosphere, in order that it may subsequently be trans- 

 ferred to the measuring- vessels. 



The explosion-vessels which I used were made according to 

 the directions of the late Lieut. -Colonel Ebner, and consisted of 

 hollow cast-iron cylinders closed at one end, while at the other 

 was a nut through which the arrangement for a galvanic explo- 

 sion passes. For this purpose the nut is provided with an exca- 

 vation in which is a thin platinum wire fastened on the one hand 

 to the insulated copper wire, and on the other to the copper wire 

 which passes directly through the nut. . Outside the cover the 



