THE LAW OF BURNING OF MODIFIED CORDITE. 



253 



a quicker rate than it can get away at atmospheric pressure. The pressure inside 

 the tube therefore rises to some point at which it bursts out explosively, the tube at 

 the same time being projected in an opposite direction. This action goes on to such 

 an extent that holes are often blown through the walls of the tube. 



On firing M.D.'f. in a gun, when any unconsumed is blown out I have often found 

 tubes with these holes or splits in their walls. The distance between these holes is 

 generally exceedingly regular. It is therefore clear that under certain conditions an 

 excess pressure exists inside the tube, even when burning under pressure, i.e., 

 explosively. 



Now, from the nature of my law of reduction, it follows that if an excess pressure 

 exists inside the tube more cordite will be burnt in a given time. There is thus 

 a reaction of cause and effect, and the internal excess pressure of itself tends to raise 

 the inside pressure more rapidly. When the gas so formed escapes into the vessel it 

 in turn raises the pressure existing in the vessel, and an increased rate of combustion 

 is the consequence. 



The time rise on fig. 6 very clearly shows this acceleration of the rate of burning. 

 Since I saw no reason why there should be a departure from my fundamental law, 

 my efforts were directed to determining what the excess internal pressure was and on 

 what it depended. The principle adopted was as follows : 



The time rise gives the average and end pressure of any interval. The outsides of 

 the tubes are burning under the cord law and produce a certain quantity of 

 gas in the interval which can be calculated. The total amount of gas produced 

 is know;i from the end pressure. The difference between these two amounts 

 of gas has come from the inside of the tube, and hence the amount of cordite burnt 

 from the inside can be calculated. Referring to Table B, we determine what pressure 

 the inside of the tube must have been burning under to consume that amount of 

 cordite in the time. From this the excess internal pressure is calculated. 

 The results of the calculation for Batch 88 are subjoined : 



