118 ANNUAL OF SCIENTIFIC DISCOVERY. 



zle-loading Indian gun it equals about 13 minutes. The difference 

 is probably due to the projectile taking a longer time to pass 

 through the core of the breech-loading gun. It may be men- 

 tioned that when the gun is swung as a pendulum and fired with 

 its axis horizontal, the shot strikes below the level. 



CUTTING UP LARGE IRON SHAFTS. 



The Buffalo correspondent of the "New York Tribune" 

 writes: "It is frequently very difficult to break up great shafts 

 of cast iron when, necessary to prepare them for the furnace. 

 Old cannon have, therefore, sold low. Upon some, powder and 

 nitre-glycerine have been tried in vain. Some have been burst 

 by ice, others by wedges driven by machinery or long-continued 

 hard labor into the muzzle. Here they are cut in two by a con- 

 tinuous stream of molten iron, which wears away the iron as a 

 stream of hot water would eat into a mass of ice. The gun is 

 rolled upon a frame in front of and level with the furnace mouth. 

 Then the muzzle end is shoved in as far as possible among other 

 iron, the opening filled up and luted around the gun, the end of 

 which is melted off. At the next charge it is shoved in another 

 length, and is thus reduced until the breech can finally be rolled 

 in and thus finished without any more expense than with pig or 

 scrap iron. 



AN EIGHT-TON STEAM HAMMER. 



The Landore Steel Works have erected a single-acting steam 

 "hammer, the head of which weighs 8 tons. The cylinder is 30 

 inches in diameter. The anvil block, which is cast in one solid 

 piece, weighs 75 tons. 



CORROSION OF IRON WATER PIPES. 



Two wrought-iron -pipes, 7 feet in diameter, have been laid on 

 the aqueduct bridge by which the Croton water is carried over 

 the Harlem River, and much trouble has been experienced from 

 their rusting, but on examination it appears that at each joint, 

 where a lap of some 15 inches is made, no notable amount of 

 rust is formed on the entire belt under the lap. It was, at first, 

 supposed that some molecular change, produced by the riveting 

 (which is double), was the origin of this protection, but this idea 

 is opposed by the fact that the rivets in other parts show no such 

 action, and that the protection in the laps is not concentric with 

 the rivets, but stop abruptly with the edge of the lap. Mr. Graff 

 also informs us that the plan of painting the pipes, when hot, 

 with boiled coal tar, has met with uniform success in his experi- 

 ence, and also at Boston, where very serious difficulty was before 

 experienced by stoppage from accumulation of rust. An attempt 

 to protect the Croton pipes by strips of zinc entirely failed. 

 Journal Franld'ui Institute. 



