Experiment With A Sub-marine Gun

Scveral experimenta with a sub-uiariiie gun have reeently been made 'it fcimp son's dry doek, East Boston, and they clearly demónstrate the feasibility of penetrating mailed vesscls belöw the water line and mail. They wcre made upon a pjan deviscd by Mr. Joscph P. Woodbury. The gun used was a brass twelvepounder through ap aperture in one of' the doek gates. The target, consisting of a mass of spruce plank about two aud a half feet thick, was suspended in the water about ten feet froiu the projeotile, and about six feet below the surface. luto this mass oí plank, with two and a half pouuds of powder, the projectile was driven twenty-one inches. A contract has betn raado with the Atlantic Works, East ]joaton, to build a small ron gunboat to be used with a gub-marine gun. It is proposod to have the gun plaeed n the bow of the vesstl. The cannon is to be of the usual shape, but much lonaer than common, and eau be cast to discharge any projectile now in use. The gun whcu ready for action, has a tin cylindrical case ütted closely at the muz.le, reudering the chamber air-tight, and prevcnting the entrance of water. When the piece is fired, the .charge attains its velocity bcfure reaehing the tin canister previously ip.cntioncd, and an cifeetive shot may bo made at a distance of two or three hundred feet. The cannon Í8 fitted into a stuffingbox, similar to that of a piston of a steam .engino, and an autotnatic port-hujo opens and shuts as the piece is run out or withdrawn. Tlio recoil of tho gun is so strong, and the action of the port is so sudden, that it is expected very little water will be shipped as the canuon will be drawn in. The pieco being breech: loading, tho water whieh cuters the muzzle is easily disposed of, aud Mr. Woodbury claims that it can be fired again in the spa.c.e of three to five minutrs. The effect of a shot tVom eight to ten feet below the water line wQulql s'uik any sliip vet