MECHANICS AND USEFUL ARTS. 81 



blow. I am persuaded a man in the gun-room of the steam-ram 

 could hardly know that a collision had taken place. It is again said 

 that the application of the principle of the steam-ram has never been 

 tried. I point out, as my answer, the cases of collision I have al- 

 luded to. Every steam-vessel that has destroyed another by run- 

 ning into that vessel is, to all intents and purposes, a steam-ram. 



The steam-frigate has only one apparent advantage over the 

 steam-ram, and that will disappear on examination ; namely, the line- 

 of-battle ship's masts and sails enable her to make long voyages ; but 

 the steam-ram has her five or six schooner masts, and, if required 

 for a long voyage, topmasts, gafftop sails, staysails, and square sails 

 can be added, so that she will spread almost as many yards of can- 

 vas as the line-of-battle ship. To resist invasion or protect seaports 

 and harbors, the steam-ram is ten times more serviceable than the 

 steam-frigate or any other description of vessel or shore battery. 



RESISTANCE OF IRON AND STEEL PLATES TO PROJECTILES. 



In England, no experiments on a very large scale, to determine 

 the resistance of iron and steel plates to the most recently devised pro- 

 jectiles, have yet taken place. The great expense necessary to incur 

 to conduct target experiments on a large scale has had, probably, 

 much to do with the delay. A committee of eminent ship-builders has 

 lately estimated that the cost of a target large enough to test half a 

 dozen modes of construction would be no less than forty-five thousand 

 pounds, and another forty-five thousand pounds would have to be 

 expended in the construction of a floating hull on which to place the 

 target. Several series of experiments, of great interest, have, how- 

 ever, been made by a government commission, of which Sir John 

 Hay was chairman, and Mr. Pairbairn a member. In the first in- 

 stance, the experiments looked to a solution of the problem as to the 

 superiority of forged or rolled armor plates for iron-clad ships ; and 

 the plates used were forged from scrap iron at the government works 

 at Portsmouth dockyard. Each plate, when fired at, was placed in 

 a vertical position against a wooden frame-work. The first plate 

 tried was a 61-inch, seven feet in length by three in breadth, and 

 weighing 49 cwt. 1 qr. The weapon used against it was the Arm- 

 strong gun, with a 126-lb. projectile. The range was four hundred 

 yards. The first shot discharged made an indentation of two inches, 

 with a slight fracture. The second made a like indentation about 

 six inches from the preceding shot, and fractured the plate on its 

 reverse. The third and fourth shots cut pieces out of the plate's 

 edge, and the fifth struck the plate about two feet from its lower 

 edge, and broke it where it had been fractured by the second shot. 

 The next plate put up was a 4|-inch, of the same length and breadth 

 as the 61-inch, and weighing 35 cwt. 2 qrs. The first shot, discharged 

 from a 100-pounder, at a range of four hundred yards, partially im- 

 bedded itself in the plate and remained there. The succeeding shots 

 at this plate were made with the 126-lb. projectile, the first striking 

 the plate in the vicinity of the lOOlb. shot, and breaking out a piece 

 of the plate of a triangular form. The succeeding shot fractured the 



