MECHANICS AND USEFUL ARTS. Ill 



"In this important discovery, as also in other matters discussed 

 in his hitest memoir, we are gratified to see, that, although now 

 carrying the weiglit of morethan three-score-and-ten years, our 

 veteran colleague still keeps the lead, which he gained at the 

 start, of his competitors in this race of improvement. 



"So completely do these three improvements cover the ground, 

 that, if the works of all other inventors who claim a shai-e in the 

 great gun of the nineteentli century were lost, the gun could be 

 restored (rifling excepted) from Mr. Treadwell's papers alone." 



CASTING OF A TWENTY-INCH CANNON. 



» 



Another twenty-inch gun was recently cast at the Fort Pitt Iron 

 Works, Pittsburg, Pa., being the third one of that size. This is 

 the first naval gun, however, and is intended for the " Puritan," 

 consort of the "Dictator," both ocean monitors. The two pre- 

 viously cast were army guns. They ai"e Rodman guns, that is, 

 cast with a water-cooled coi-e. 



The quantity of metal melted at once was enormous ; not less 

 than 140,000 j^ounds, and three fui-naces were in use to accom- 

 plisli it in time, the fires being started at 4.30 A. m. on the morn- 

 ing of joouring. The iron was in the following proportion : 

 101,000 Juniata, second fusion ; 39,000 Juniata pig, from the 

 Bloomfield furnace : tliis is stated to be the finest quality of metal, 

 for gun founding, in the countrj". The furnaces were tapped at 

 12.10, and the mould was filled in a short time. 



The length of the rough casting is 236 inches. The maximum 

 diameter is 65^ inches, and the minimum 48 inches. When fin- 

 ished, the breech of the gun will measure 64 inches in diameter, 

 and the nozzle 35A inches. The length of the cylinder bore is 

 147 inches, depth of chamber 10 inches. The thickness of metal 

 outside the bore, at the breech, is 22 inches, and at the nozzle 

 7 9-10 inches. . Diameter of trunnion 18 inches. At 9.20, Sunday 

 morning, the water was turned oft", at which the temperature was 

 97°. The core l)arrel was hoisted, when it came out ijerfcctly 

 clean, there being every indication of perfect success in the cast- 

 ing. After the barrel was hoisted out, a very small sti'eara of 

 water was allowed to flow into the bore, when it immediately 

 became steam. Tliis was to he continued until 8 o'clock, when 

 a column of cold air would be forced in, and the cooling process 

 completed in this way. — Scientific America?!,. 



THE PALLISER GUN. 



Last August, four Palliser guns were tested with perfect success 

 at the proof butt in the Royal Arsenal at Woolwich, under the 

 superintendence of Lieutenant-Colonel Freetli, Assistant Superin- 

 tendent of the Royal Gun Factories. These guns were formerly 

 cast-iron 32-pounders and 24-pounders, and have been converted 

 into 64-pounders and 56-pounders, at Elswick. Twenty more of 

 these guns arrived the same day at Woolwich, and will at once 

 be sent to proof. A 64-pounder Palliser gun has also undergone 



