88 ANNUAL OF SCIENTIFIC DISCOVERY. 



pared with the inadequate cohesive force of the metal at the place 

 struck, together with the incompressible nature of the material, fur- 

 nishes a ready explanation of the cause of the fractures which have 

 resulted from heavy charges of powder at short ranges with the x solid 

 English targets. 



" Having attentively studied the subject, and demonstrated satis- 

 factorily the cause of the unexpected destruction of the enormous 

 solid targets, the expedient at once suggested itself to the writer, of 

 applying a laminated protection in order to exhaust the vis viva of 

 the shot, by degrees, before reaching the solid blocks intended as the 

 real armor. The peculiar feature of the laminated protection is evi- 

 dently that each successive lamina, or plate, may be split without 

 affecting the next ; forming, as it does, a separate body placed at a 

 measurable distance from the neighboring plate. Not so with a solid 

 projectile ; a split or crack of sufficient width must inevitably owing 

 to the incompressible nature of the material run through the entire 

 substance. Hence the destruction of the enormous blocks of wrought 

 iron tested in England. 



"The condition of my 15-inch target, recently tested by Captain 

 Dahlgren, at the Washington Navy Yard, proves incontestably that, 

 by interposing a laminated protection, armor may be made absolutely 

 impregnable. Not only are the 5-inch wrought slab and the backing 

 of 4-inch plating together nine inches completely uninjured; but 

 there remain also in the centre of the indentation made by the shot, 

 more than two inches thickness of the outer plating. The absolute 

 protection thus afforded by the 6-inch thick plate lining to the 5-inch 

 wrought slabs of the 15-inch target, placed close to the muzzle (34 

 yards) of an 11-inch Dahlgren gun, fired with 30 pounds of powder, 

 proves conclusively that the side armor of the Puritan and Dictator 

 will be impregnable. This side armor, it will be remembered, is 

 composed of 6-inch plating, under which is inserted the longitudinal 

 wro light-iron slabs (stringers), backed by the 4-feet thickness of oak, 

 firmly attached to the side of the ship without, the employment of the 

 objectionable through-bolts employed in the Warrior and other 

 European iron-dads.'' 



Resistance of Iron Plates to Heavy SJtf>t. Mr. Scott Russell, from 

 the result of the various experiments that have been made by the 

 British Government, deduces the following thicknesses of iron-plates 

 as proof against shots of various weights. For the present: the 

 4-inch plate against the 68-pounder ; ('4-inch plate against the 136- 

 pounder; 7^-inch against the i ; 0(!-pounder ; and 8^-inch against the 

 270-pouruler. For the future : the 10-inch plate against the 400- 

 pounder; 11-inch against the 500-pounder; and 12-inch against the 

 600-pounder. These results, Mr. Kussel states, are entitled to our 

 full confidence, as the experiments at Shoeburyness fully bear them 

 out. 



New Experience with Iron-clad Vessels in Action. Some addi- 

 tional experience in the value and working of iron-clad vessels in 

 warfare, has been gained during the past year from a conflict which 

 took place in the Bay of Mobile, between a formidable iron-clad 

 Confederate ram the Tennessee and a fleet of wooden vessels of 

 war and monitors, under the command of Admiral Farragut.of the 



