involved in the Construction of Artillery. 



P 



// 

 L ' 



271 



(61) 



L being the length of the chase, or ratlier of that part of it passed through by 

 the shot, is equal to the mean effort of the charge. This mean effort, and the 

 pressure per square inch due to it, is always below the maximum mean effort, 

 or pressure, and the latter is most in excess of the mean, where tlie lengtli 

 of the gun is greatest. Hence, comparisons of mean pressure for gunpowder 

 and gun-cotton will be nearest the truth when taken for the shortest trajects 

 within the gun, or at moments nearest to that of ignition. 



The following Table gives the velocity, vis viva, and mean effort, due to 

 gunpowder and gun-cotton, within the limits tried : — 



Table XIII. 



The Dimensions are in Metres, the Weights in Kilogrammes. 



248. It results from these experiments, that the velocity of the shot does 

 not increase beyond 49 calibers ; that at 64 calibers the velocities are equal for 

 gunpowder and gun-cotton, and at greater length of chase the latter would begin 

 to lose velocity; that the mean maximum effort of the gun-cotton, constantly 

 increases, above that of the gunpowder, in proportion as the length of the chase 



2 n2 



