The long serirs of experiments and discussions in England on this subject scem to Itave resulted in the adoption of the following conclusions:— 1st. A cannon ball wiII pass through almost any number of thicknesses of boiler plate which are merely riveted together. 2d. Wrought iron, 4k inches thick, welded into solid plates, will rcsist any shell, and they will resist any ,olid shot striktng only once in the same place ; but a succession of solid shots strikil:g the same plate will break it in pieces, causing great destruction to the ship. 3d. Wooden ships plaited with iron are terribly shattered by shot striking the plates, when the plates are not pierced by the ball. As vessels plated with 4!-inch iron are very top heavji, it is necessary that they shoulU have great breadth of beam or they will founder in a rough sea; and as, with breadth of beam, they must be very long in order to mnke them sharp enough for sreed, it follows that none but large vessels are suitable forcarrying iron armor. In accordance with these conclusions, the British government is now building cnormous iron ships for their navy, to be protected by 4k-inch iron plntes. One of these—the Warrior—is nearly completed. She is larger than any vessel afloat, with the single exception of the Great Eastern, being 420 feet long lind measlll'ing 6,117 tuns British measurement. We shall publish a minute description of her in our next number.STOPPING LEAKS IN STEAM PIPES.—In factories heated with steam, the iron pipes rust inside, and this,-in the course of time, eats through the metal and forms leaks in several places. A correspondent writing to us from Sandersville, N.Y., informs us that he has effectually Slopped a number of such leaks in a long pipe, Inputting an iron clasp on each with a piece of yulcaniz('d' india-rubber under it. This saved the expense of getting a new pipe for a long time aftcr the old one commenced to leak. \Ve have found a piece of sheet lead, scraped bright on the inside, very effectual in stopping a leak in a steam pipe, when drawn tight by a screw clasp.