involved in the Construction of Artillery. 261 



conceptions. The results, however, of the experiments (at which the author 

 was present), very rapidly dispelled all ignorance of the subject, and fully 

 justified the conclusion, come to by Government, that plate-iron ships, as then 

 (and still) constructed, are unsuited to the purposes of war M'henever they may 

 be exposed to shot. At low velocities, the laceration of the rivetted seams, and 

 utter dislocation of the bolts connecting the opposite sides of the double-plated 

 targets, was conclusive as to the fate of an iron ship (although prepared with 

 12 inches thick of India-rubber and cork lining), if exposed to a few rounds of 

 large shot, fired at a very moderate velocity. In a scientific point of view, 

 however, the most remarkable and important phenomena were elicited by the 

 effects upon the plates of the shot fired with full service charges, and having a 

 velocity probably not much under 2000 feet per second. 



The effect on the plates, which were about half-inch thick, and of fine tougli 

 iron of the best quality, was to strike out an almost perfectly circular hole, a 

 little larger in diameter than the shot, with scarcely any burr or bending of the 

 edges, which were broken off sharp and square, and presented all round a large, 

 well-defined, crystalline fracture, the planes or facets of the crystals very gene- 

 rally being disposed tangentially to the circumference, and perpendicularly to 

 the plane of the plate. The piece struck out was shivered into fragments, 

 seldom having a surface of above three or four square inches each, and all 

 whose edges also were sharp, square, and crystalline, with the greater number 

 of the planes of crystallization nearly parallel to the lines of fracture. The 

 temperature of the pieces struck out and the iron around the aperture was 

 raised, by the sudden rupture and change of form, from that of the atmosphere, 

 to one so hot, that the fragments, when picked up at the butt, after having flown 

 about 150 yards through the air, could not be handled with the naked hand, 

 and in several cases the heat was sufficient to " blue" the surface of fresh metallic 

 fracture. 



227. Whence did this arise? Why should the velocity of the blow change 

 the nature of the fracture of the broken body ? — for there can be no doubt that 

 any one of those plates broken by bending slowly backwards and forwards, or by 

 striking over an anvil with the moderate velocity of a common sledge-hammer, 

 would have been with great difficulty, broken at all, and would at length have 

 presented a long and irregularly fibrous or very partially crystalline fracture. 



VOL. XXIII. 2 M 



