PROCEEDINGS OF THE POLYTECHNIC ASSOCIATION. 563 



introduced into the gun. At the moment of discharge the cap 

 is driven home on the body of the shot with great violence, and 

 forces out the lead to a sufficient extent to tightly fill all the 

 grooves. Any excess of pressure above that desired is prevented 

 by the contact of the cap with the cast iron body of the shot. 

 The most approved form of this shot makes the lead belt very 

 narrow. The specimen ball exhibited, which was 2^ inches in 

 diameter, and 5\ inches long, was encircled by a lead belt only 

 five-eighths of an inch wide and one-quarter inch thick. The 

 ball is supported in the gun, not on this belt alone, but by it 

 and by a nicely turned ring or surface of a proper diameter at 

 the extreme rear. A small quantity of tallow or other grease 

 was placed in front of the lead belt so that the compression of 

 the lead forced out the grease in front. Lead alone is of a 

 greasy character, but it was preferable to lubricate slightly. 



There was, he said, even in this ball, a strong disposition of 

 the lead to fly off or separate from the iron, but the force was 

 slight in comparison with the other mode of expansion. The 

 centrifugal force due to the rapid rotation was the only force 'to 

 be resisted in this case. To insure against this Mr. Hotchkiss 

 made his lead rings thus narrow, and also constructed his iron 

 parts in such form that they hooked on, and thus aided to confine 

 both the front and rear edge of the belt. If this bullet was cut 

 into many pieces or segments the fragments would probably all 

 be retained. 



The inertia of the ball in any heavy rifled ordnance offered 

 great resistance to the rotary or twisting motion, and there was 

 always a risk that the lead belt would twist about on the iron 

 without imparting a proper rotary motion to the iron body. To 

 avoid this various means had been devised. One inventor had 

 caused his belts to jog or notch into the iron at intervals on the 

 front and rear edges. Another had made deep undulations in 

 the iron under the belt. By either of these means the lead could 

 obtain a very firm grasp on the iron. 



Visitor. — Has the Hotchkiss ball a superiority over all others ? 



Mr. Stetson thought it had. 



Visitor. — Is it used only for cannon ? 



Mr. Stetson. — Yes. I think the practice of the United States 

 Government of rifling ordinary cannon which were less strong 

 than cannon should be for such purpose, would cause hollow 

 shot to be used generally in such instead of solid balls. 



