102 ANNUAL OF SCIENTIFIC DISCOVERY. 



which the water poured in torrents. A shell, with percussion fuse, 

 burst in entering, opening up a chasm of five feet by three in the 

 planking, shattering the ribs and bursting up the deck beams above." 

 New Mode of JRi/Hn;/ Guns. Xo general principle of rifling guns 

 seems to be recognized and practiced. 



Regular and increasing twists of various pitch are used by rifle 

 makers for guns of the same bore. Capt. T. A. Blakely, the inventor 

 and constructor of the best guns of large caliber in Europe, has taken 

 out a patent for the application of a new principle. It consists in rifl- 

 ing guns and forming projectiles in such a manner that the s:i;n;' power 

 shall always act uniformly. The patentee first decides at what distance 

 from the center of the projectiles the turning force of the spiral shall 

 act, and the smaller the bore the nearer the center it acts. He says : 

 " Let a circle be now drawn, with a center in the axis of the barrel, 

 the radius of which circle is this settled distance ; then form the rilling 

 of such a shape that a line perpendicular to any point of its surface 

 shall also be a tangent to this circle." The projectiles are formed to 

 correspond and follow the same mathematical rules with respect to 

 the shape of their external surfaces. 



Oun-Cotton. A committee of the French Academy, consisting of 

 M. Al. Pelouze and Maurey, appointed to consider the applicability 

 of gun-cotton to ordnance, do not by their report at all agree with the 

 conclusions of the Austrian or English experimenters, (see Annual of 

 Sci. tiis. 18G4). Contrary to the assertions made by the Austrian Gen- 

 eral Leuk, that his gun-cotton does not explode at a lower temperature 

 than loG, Centigrade, they affirm that all their specimens exploded or 

 were otherwise decomposed at a temperature of 100 ; and that at a 

 temperature as low as 55, decomposition ensued with equal certainty, 

 but only in the course of a few hours. In one case they even obtained 

 an explosion at 47, which induces them to suspect that it may even be 

 decomposed at the common temperature. Upon the whole, therefore, 

 tiiey do not recommend the substitution of gun-cotton for gunpowder 

 in the French service. 



Wrought-Iron Forts. There has been recently constructed in Eng- 

 hnd, for the Itussian Government, a massive iron structure, which is 

 intended to serve as a sort of shield, or outer protection to the face of a 

 tort or rampart in the harbor of Cronstadt. Its structure is as follows : 

 It is 43 feet six inches long by ten feet in bight, and is composed of 

 wrought-iron bars of a size hitherto unattempied in " grooved rolls," 12 

 inches by 12 inches, rolled with a " rebate," and corresponding hollows 

 on the opposite side, strengthened by dovetailed ribs at their back, three 

 inches in thickness, which are attached by keys or wedges hi dovetailed 

 holes to upright beams or girders, 14 inches by 14 inches, on each side 

 of the embrasures and at the ends, and in two equal divisions of its 

 length, to f .ur frames or brackets like the letter A, with one vertical 

 side. The foundation plate on which the whole structure stands is 43 

 feet six inches long, t\vo feet wide, and 3 inches thick, rolled in one 

 length. The total weight of the shield is about 140 tons. Each em- 

 brasure is four feet from the platform, and four feet high. In the throat 

 it is two feet two inches in width, cr, with the shelving of the cheeks, 

 two feet ten inches. The military advantages of such an opening in an 

 iron parapet of 15 inches thickness is, that the guns can be worked so as 



