THE ROYAL ARTILLERY INSTITUTION. 
385 
Hence the deoxidation of nitrogen-compounds during the combustion takes 
place the more completely the greater the work which the gun cotton has to 
perform during its combustion. 
This circumstance suggested to me the idea of exposing the gun cotton 
during its combustion to a determinate resistance, and regulated so that it 
just gives way at the moment the gun cotton is completely burnt away. This 
condition led me to the experiment of placing a vessel filled with gun cotton 
which offered the necessary resistance, in a 60 -pr. mortar, which was then 
exhausted and the gun cotton exploded by galvanism. 
The detailed plan of this apparatus is seen from the diagram. In the 
touchhole of the mortar a strong iron nut, a , is screwed, which by the aid of 
a good stuffer, e, enables the mortar to be made air-tight. The screw is 
provided at b with a short tube closed by a cock, by which the vacuum is 
obtained in the subsequent operations. At d' a copper wire, well insulated 
with gutta percha, passes through the nut, while at d is a small hook; to this 
and to the insulated copper wire the vessels filled with the gun cotton intended 
for explosion are fixed, and, as the figure shows, allow the ignition of the 
charge to be effected. In the experiment the mortar is exhausted, the tap 
closed, and the platinum wire in the charge ignited by the current from six 
Smee's elements, and thus the vessel burst. It is readily seen 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. 
