08 philosophical transactions. [anno 178 1. 



therefore to be greater in the former case than in the latter, as I found by expe- 

 riment. But to make this matter still plainer, we will suppose any given quan- 

 tity of powder to be confined in a space that is just capable of containing it, 

 and that in this situation it is by any means set on fire. Let us suppose this 

 space to be the chamber of a piece of ordnance of any kind, and that a bullet, 

 or any solid body, is so firmly fixed in the bore immediately on the charge, that 

 the whole effort of the powder shall not be able to remove it. As the powder 

 goes on to be inflamed, and the elastic fluid is generated, the pressure on the 

 inside of the chamber will be increased, till at length, all the powder being burnt, 

 the strain on the metal will be at its greatest height, and in this situation things 

 will remain, the cohesion or elasticity of the particles of metal counterbalancing 

 the pressure of the fluid. Under these circumstances very little heat would be 

 generated; for the continued effort of the elastic fluid would approach to the 

 nature of the pressure of a weight ; and that concussion, vibration, and friction, 

 among the particles of the metal, which in the collision of elastic bodies is the 

 cause of the heat that is produced, would scarcely take effect. 



But instead of being firmly fixed in its place, let the bullet now be moveable, 

 but let it give way with great difficulty, and by slow degrees. In this case, the 

 elastic fluid will be generated as before, and will exert its whole force on the 

 chamber of the piece; but as the bullet gives way to the pressure, and moves on 

 in the bore, the fluid will expand itself and become weaker, and the particles of 

 the metal will gradually return to their former situations; but the velocity with 

 which the metal restores itself being but small, the vibration that remains in the 

 metal, after the elastic fluid has made its escape, will be very languid, as will be 

 the heat that is generated by it. But if, instead of giving way with so much 

 difficulty, the bullet is much lighter, so as to afford but little resistance to the 

 elastic fluid in making its escape, or if the powder is fired without any bullet at 

 all; then, there being little or nothing to oppose the flame in its passage through 

 the bore, it will expand itself with an amazing velocity, and its action on the 

 gun will cease almost in an instant, the strained metal will restore itself with a 

 very rapid motion, and a sharp vibration will ensue, by which the piece will be 

 much heated. 



Of the effect of ramming the poivder in the chamber of the piece. — The charge, 

 consisting of 218 gr. of powder, being put gently into the bore of the piece in 

 a cartridge of very fine paper, without being rammed, the velocity of the bullets 

 at a mean of the 40th, 41st, 42d, and 47th exper., was at the rate of 1225 feet 

 in a second; but in the 68th, 69th, and 70th exper., when the same quantity of 

 powder was rammed down with 5 or 6 hard strokes of the ram-rod, the mean 

 velocity was 132Q. feet in a second. Now the total force or pressure exerted by 

 the charge on the bullet is as the square of its velocity, and 1329* is to 1225' 2 as 

 1.1776 is to 1 ; or nearly as 6 is to 5; and in that proportion was the force of 

 the given charge of powder increased by being rammed. 



