Experiments upon Gunpowder. 91 



impinged against it with a velocity of 428 feet in a sec- 

 ond. 



If we now suppose that the force of aurum fulminant 

 arises from the action of an elastic fluid, that is gener- 

 ated from it in the moment of its explosion, and that the 

 elasticity of this fluid, or rather the force it exerts upon 

 the bullet as it goes on to expand, is always as its dens- 

 ity, or inversely as the space it occupies ; then from the 

 known dimensions of the barrel, the length of the 

 space occupied by the charge (which in this experiment 

 was 0.47 of an inch),, and the weight and velocity of 

 the bullets, the elastic force of this fluid, at the instant 

 of its generation, may be determined : and I findj upon 

 making the calculation upon these principles, that its 

 force turns out 307 times greater than the mean elastic 

 force of common air. 



According to Mr. Robins's theory, the elastic force 

 of the fluid generated from gunpowder in its combustion 

 is 1000 times greater than the mean pressure of the at- 

 mosphere ; the force of aurum fulminant, therefore, ap- 

 pears to be to that of gunpowder as 307 is to 1000, or 

 as 4 is to 13 very nearly. 



Of the Specific Gravity of Gunpowder. 



To determine the specific gravity of gunpowder, I 

 made use of the following method. A large glass buck- 



o o o 



et with a narrow mouth being suspended to one of the 

 arms of a very nice balance, and counterpoised by 

 weights put in the opposite scale, it was filled first with 

 government powder poured in lightly, then with the 

 same powder shaken well together, afterwards with 

 powder and water together, and lastly with water alone, 

 and in each case the contents of the bucket were very 

 exactly weighed. 



