the Force of Fired Gunpowder. 123 



bore, was covered with a circular plate of gold, in order 

 the better to defend the mouth of the bore against the 

 effects of the corrosive vapour, yet this plate being 

 damaged in the course of the experiments (a piece of it 

 being blown away), the remainder of it was removed ; 

 and it was never after thought necessary to replace it by 

 another. 



When this plate of gold was taken away, the length 

 of the barrel was of course diminished as much as the 

 thickness of this plate amounted to, which was about 

 Tly o" P art f an i ncn but in order that even this small 

 diminution of the length of the barrel might have no 

 effect on the result of the experiments, its bore was 

 deepened -j-jy-g- of an inch when this plate was removed, 

 so that the capacity of the bore remained the same as 

 before. 



After making use of a great variety of expedients, the 

 best and most convenient method of closing the end of 

 the bore, and defending the flat surface of the steel 

 hemisphere from the corroding vapours, was found to 

 be this : first, to cover the end of the bore with a cir- 

 cular plate of thin oiled leather, then to lay upon this 

 a very thin circular plate of hammered brass, and upon 

 this brass plate the flat surface of the hemisphere. 

 When the elastic fluid made its escape, a part of the 

 leather was constantly found to have been torn away, 

 but never in more places than one, that is to say, always 

 on one side only. 



What was very remarkable in all those experiments in 

 which the generated elastic vapour was completely con- 

 fined, was the small degree of expansive force which this 

 vapour appeared to possess after it had been suffered to 

 remain a few minutes, or even only a few seconds, con- 



