PROCEEDINGS OF THE POLYTECHNIC ASSOCIATION. 399 



Hotclildss ; and ilie other, the recently patented cartridge case 

 of Fenwick & Moore. There is in both a wooden sabet next to 

 the projectile. The Hotchkiss cartridge case is surrounded with 

 flannel, so that, as it passes out, it sponges the gun. It is sup- 

 posed that the gun, in which this is used, Avill need no other 

 sponging. The back of the case is prevented from staying in the 

 gun, by making it so weak in certain lines that it will break in 

 those lines immediately upon the discharge, the force of the 

 powder then coming upon the back of the gun itself, and th^ 

 whole of the case passing out together. The charge is prepared 

 for firing by driving a sharp point through the vent, with suffi- 

 cient force to punch a whole through the metallic case. Fenwick 

 & Moore's cartridge case has a conical back, leaving small 

 empty chambers behind the cartridge, into which, when, the 

 powder explodes, the gas is first driven, the back of the case 

 being made weaker in two places to facilitate its escape. The 

 gas being thus introduced at once behind the metallic back of 

 the case, forces it out of the gun. It is a question whether the 

 powder exerts its maximum force with or without such a cham- 

 ber ; but it is unnecessary to make tlie chamber large enough to 

 be a disadvantage in that respect. 



Mr. Stetson. — The chamber can be reduced if it is found too 

 large. I will remark that this drawing of the Hotchkiss cart- 

 ridge-case is for a 12-inch bore, the size of the "Union," the 

 large riiled gun at Fortress Monroe. 



PROJECTILES, &C. 



The Chairman. — Can any one give us a brief description of the 

 Sawyer gun ? 



Mr. Babcock. — It is a gun of five inches bore, taken out by 

 Capt. Bartlett. It is a 24-pounder, carrying a 48-lb. shell. The 

 Sawyer shell is an elongated cast-iron projectile, coated with 

 some soft metal, on which are cast the projections fitting the 

 grooves of the gun. In placing the projectile in the gun, it is 

 necessary to place these grooves carefully ; and, in that respect, 

 it is similar to the Whitworth gun. It is stated to have thrown 

 a rifled shot 4, GOO yards, which is less than three miles. Any 

 rifled projectile could throw a shot from the Rip Raps to Sewall's 

 Point. 



The Chairman. — "Will any gentlemean give us a brief summing 



