112 ANNUAL OF SCIENTIFIC DISCOVERY. 



AN IMMENSE AIR-GUN. 



One of our most successful inventors and engineers has lateVf 

 patented, and the specification has been published, of an enot* 

 mous air-gun of 32-inch bore, to throw a 6,000-pound shot. The 

 bore of the gun is to be upwards of 30 feet long, and the inventor 

 asserts that he can compress and retain air at a working pressure 

 of 10,000 lbs. per square inch. The sectional area of a 32-inch 

 bore is 804^ square inches, and the totctl initial pressure would 

 thus be 8,042,400 pounds, or nearly 3,600 tons. It would, of 

 course, be next to impossible to pump in air fast enough at this 

 enormous pressure to keep up the velocity of the shot, so the 

 high-pressure air is to be contained in a huge casing or jacket 

 formed around the bore of the gun, and having the same capacity 

 of, say, 165 cubic feet. Thus, instead of the pressure being re- 

 duced almost to nothing at the muzzle, the air would have been 

 expanded but twofold on the discharge of the shot ; and if we 

 disregard the influence of rarefaction, and consequent cooling by 

 eximnsion, and its effect on the pressure, we should have 5,000 

 pounds per square inch still left. If we take the average pressure 

 at 7,500 pounds, throughout the length of the bore, we shall have 

 2,400 tons exerted through 30 feet, or say 72,000 foot-tons, and 

 this, were the air to follow fast enough, would send a 6,000-pound 

 shot at a rate of more than 1,300 feet per second. As no ordinary 

 valve could be opened quickly enough to admit air under such 

 pressure, and in such quantities, the shot itself forms the valve. 

 The high-pressure air in the air casing or jacket enters the cham- 

 ber of the gun through ports, like those by which steam enters a 

 steam-cylinder. The shot — a short cylinder, with hemispherical 

 or pointed ends — is so packed as to close these ports while the 

 jacket is being pumped full. To discharge the gun a little high- 

 pressure air is separately pumped in behind the shot, so as to start it 

 on and past the ports, when the stored-up air does the rest of the 

 work. 



Although there may be certain practical difficulties in carrying 

 out this scheme, it possesses great interest, and we shall look with 

 much curiosity to its practical realization. — Engineering. 



HAND AND SHOULDER GUNS. 



Mr. Charlesworth read a paper, at the last meeting of the British 

 Association, on the substitution of hand for shoulder guns. He 

 exhibited a gun, invented by himself, its peculiarity consisting in 

 its being used in the hands, extended from the body, instead of 

 being rested against the shoulder. The first hand-gun he had 

 known was a stick-gun, invented by Mr. Hubbard about 45 j'ears 

 ago, but the difficulty which could not be overcome in respect to 

 that weapon Avas the recoil. The principle he had applied to the 

 hand-gun was what he termed the elevation, — a handle which 

 screwed into a strong piece of iron on the lower x^ortion of the 



