MECHANICS AND USEFUL ARTS. 87 



results : The first fourteen rounds were fired at a distance of six hundred 

 yards, and, after the first few rounds, the timber work gave way in several 

 directions. The last ten rounds were fired at a distance of four hundred 

 yards, and the work of destruction commenced was thus consummated. The 



v 



timber work of the target was completely broken and splintered, and the 

 plates of iron made by the rolling process were cut up and split, having ap- 

 parently but little adhesion. The iron plates which had been made by the 

 old process resisted the solid wrought iron shot much more successfully, and 

 it was apparent that these plates possessed more adhesive power than the 

 rolled plates. Such was the tremendous force of the cannonade that the 

 immense target was forced by the concussion several feet from the founda- 

 tion or box on which it was placed. The last shot fired was the most effec- 

 tive. This shot went completely through the target, timber-work and iron 

 included. It was the subject of remark by several practical men that the 

 principle of combining timber with iron plates, was, no doubt, the best that 

 could be at present adopted ; but it was evident from these experiments that 

 such plates must be improved upon before they could resist the concussion 

 of repeated discharges of heavy shot. 



ON THE STRENGTH OF IRON ORDNANCE. 



During the past year, some interesting trials of the strength of heavy 

 ordnance, manufactured by Alger, of Boston, for the United States Navy, 

 have been made under the direction of the Department. One of a number 

 of nine-inch calibre iron guns was selected as a sample for undergoing the 

 test required per contract, namely, that they should endure one thousand 

 rounds, of ten pounds of powder, and a projectile of seventy-two pounds. 



The result of the trial was, that the gun in question stood 1,500 rounds 

 with so slight an effect that it would probably endure another thousand, and, 

 as the rest of the lot were made of the same iron, and under precisely the 

 same circumstances, they are presumed to be of the same character. 



ON THE CONSTRUCTION OF THIRTY-SIX-INCH MORTARS. 



At the last meeting of the British Association, Mr. K. Mallett presented a 

 communication on the above subject. The largest shells, said Mr. M., with 

 few exceptions, used during and up to the late war, were thirteen-inch shells, 

 of about 180 or 200 pounds weight, and holding about nine pounds of 

 powder. The depth to which this shell would sink in compacted earth was 

 about thirteen feet, but it was incapable of piercing masonry beyond 

 eighteen or twenty inches, except by repeated shots, and was fired at a range 

 of 4,700 yards. It had occurred to him. as very desirable that a shell should 

 be thrown at much greater range with greatly increased power of demolition 

 and penetration ; and he came to the conclusion that a shell of less than 

 three feet in diameter would not answer the purpose, and he found that such 

 a shell, holding five hundred pounds of powder, would become not so much 

 an instrument by which human life would be taken, as a mine or series of 

 mines, transferred into fortifications, piercing compacted earth to a depth of 

 fifteen feet, and demolishing solid masonry at many times the distance at 



