Were a smuotli bore. 



^1 



PROCEEDINGS OF THE POLYTECHNIC ASSOCIATION. 439 



be readily reduced by a file, or any other suitabbi 

 tool, so as to make the form practically perfect, 

 and'insure that the canister, when tightly drawn 

 together, shall be straight with very little labor in 

 the fitting. When this canister is fired from a 

 rifled gun, the castings ABC ride upon the lands 

 alone, and the whole behaves exactly as if the gun 

 The exterior of ^^C'may be finished or covered with 



cloth or paper to in- 

 duce a gentle efiect 

 on the gun, and the 

 number of the rings 

 C interposed between 

 A and B may be in- 

 creased or diminish- 

 ed, according to the 

 strength of the gun. 

 All the castings AB 

 and CO are rounded 

 on their exteriors, so 

 as to correspond in 

 form with ^ portion of 

 a sphere or spheroid. 

 This renders it impos- 

 sible for the edge of 

 any casting to come 

 in contact with the 

 inner surface of the 

 gun, and abrade it 

 under any circum- 

 stances. G G are 

 holes in the rear cast- 

 ing A, which allow 

 the gases to enter and 

 permeate among the 

 balls D, while the 

 canister is moving 

 along the bore. As 

 soon as, or before, the 

 canister escapes from 

 the muzzle, the hook' 

 bolt or wire breaks, 

 and the canister is 

 expanded lengthwise 

 by the tension of the 

 gas thus admitted, 

 through the holes GG 

 at the rear end, the 

 hook bolt E^ breaking 



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