Experiments upon Gunpowder. 37 



and in that situation be struck with a smart blow of 

 the hammer, it will be found to be much heated ; but the 

 same bullet, in the same situation, may be much more 

 flattened by pressure, or by the stroke of a very heavy 

 body moving with a small velocity, without "being sen- 

 sibly warmed. 



To generate heat, therefore, the action of the powder 

 on the inside of the piece must not only be sufficient to 

 strain the metal, and produce a motion in its parts, but 

 this effect must be extremely rapid ; and the heat will be 

 much augmented if the exertion of the force and the 

 duration of its action are momentaneous ; for in that 

 case the fibres of the metal (if I may use the expres- 

 sion) that are violently stretched will return with their 

 full force and velocity, and the swift, vibratory motion 

 and attrition before described will be produced. 



The heat generated in a piece by firing is, therefore, 

 as the force by which the particles of the metal are 

 strained and compressed, the suddenness with which 

 this force is exerted, and the shortness of the time 

 of its action; that is to say, as the strength of the 

 powder and the quantity of the charge, the quickness 

 of its inflammation, and the velocity with which the 

 generated fluid makes its escape. 



Now the effort of any given charge of powder upon 

 the gun is very nearly the same, whether it be fired 

 with a bullet or without a bullet ; but the velocity with 

 which the generated elastic fluid makes its escape is 

 much greater when the powder is fired alone than when 

 it is made to impel one or more bullets ; the heat ought, 

 therefore, to be greater in the former case than in the 

 latter, as I found it to be by experiment. 



But to make this matter still plainer, we will suppose 



