ii4 Experiments to determine 



the piece is perfectly sensible, and this time is evidently 

 shorter after the piece has been heated by repeated firing. 

 With the same charge, the recoil of a gun (and con- 

 sequently the velocity of its bullet) is greater after the 

 gun has been heated by repeated firing than when it is 

 cold. The velocity of the bullet is considerably greater 

 when the cannon is fired off with a vent tube, or by fir- 

 ing a pistol charged with powder into the open vent, 

 than when the vent is filled with loose powder. The 

 velocity of two, three, or more fit bullets discharged at 

 once from a piece of ordnance, compared to the velocity 

 of one single bullet discharged by the same quantity of 

 powder from the same cannon, is greater than it ought 

 to be according to the theory. Considerable quantities 

 of powder are frequently driven out of cannon and other 

 fire-arms unconsumed. The manner in which the smoke 

 of gunpowder rises in the air, and is gradually dissolved 

 and rendered invisible, shews it to partake of the nature 

 of steam. But not to take up too much time with 

 these general observations, I shall proceed to give an 

 account of experiments, the results of which will be con- 

 sidered as more conclusive. 



Having found it impossible to measure the elastic 

 force of fired gunpo.wder with any degree of precision 

 by any of the methods before mentioned, I totally 

 changed my plan of operations, and instead of endeavour- 

 ing to determine its force by causing the generated elastic 

 fluid to act upon a moveable body through a determined 

 space, I set about contriving an apparatus in which this 

 fluid should be made to act, by a determined surface, 

 against a weight, which, by being increased at pleasure, 

 should at last be such as would. just be able to confine 

 it, and which in that case would just counterbalance, and 

 consequently measure, its elastic force. 



