PROCEEDINGS OF THE POLYTECHNIC ASSOCIATION. 385 



to be closed. I have, therefore, retained of the barrel only the 

 bars constituting the rifling of the cannon, keeping them in place 

 by surrounding them at proper intervals with rings. These 

 bars, of course, will give the same direction to the shot as if the 

 barrel were closed, while the air passes freely through, and there- 

 fore the barrel cannot get heated. 



I have been told by many persons that the expansive force of 

 th-e powder ought to follow the ball up to the muzzle, and if 

 there were any holes in the barrel a portion of that expansive 

 force would be lost. I am not much versed in the principles of 

 artillery, but I can tell you the results of my own experience and 

 experiments. By surrounding these bars with this tight fitting 

 covering, I can convert it into a closed barrel, in which the ele- 

 ment of fraction will be precisely the same. I have charged 

 this cannon with single, double, and triple charges of powder, 

 and fired into targets made of a thousand sheets of paper, first 

 with the closed barrel, and then with the open barrel. I have 

 made these experiments before many scientific gentlemen, and 

 yesterday before three members of the Polytechnic Association : 

 Messrs. Stetson, Dibben, and C. W. Smith. I requested Mr. Dib- 

 ben to prepare the charge of powder, that he might be sure that 

 the same quantity and same kind of powder should be used in 

 both cases. We found, as these gentlemen can testify, that the 

 penetration was considerably greater witli the open than with the 

 closed barrel. This result I have found not only with this small 

 model, but with larger pieces. I have taken two Hall's carbines, 

 identically alike, opening the bai'rel of the one and leaving that 

 of the other untouched, and have found tliat the projectile would 

 come with at least as great force from that which I had opened as 

 from the other. 



The advantage of having a barrel that cannot get heated is 

 very considerable. The Armstrong gim will shoot very accu- 

 rately for a few rounds ; but the history of the Crimean, the Aus- 

 trian, and lately of the Chinese war, shows that however accu- 

 rately these and the French rifled cannon may perform at first, 

 after thirty or forty rounds the aim cannot be depended upon. 

 The reason is obvious. If the particles of metal are ever so 

 slightly expanded upon one side more than upon the other, it 

 curyes the barrel sufficiently to injure the accuracy of the aim. 

 With free ventilation, this injurious eflect cannot be produced. 



[Am. Inst.J Y 



