MECHANICS AND USEFUL ARTS. 117 



stant. The results of these experiments were very interesting, 

 and are fully detailed in the tables which accompany Captain 

 Noble's report. 



The conclusions which have been drawn from these results will 

 be given when the second point has been considered. To deter- 

 mine this question, viz., the relative resistance of a plate to 

 penetration by two shot of similar form of head, and striking with 

 " woi'k" proportional to their respective diameters, the commit- 

 tee fired a series of steel hemispherical-headed shot, of various 

 weights and diameters, at 4^ and 5^-inch unbacked wrought-iron 

 plates, the velocities being so arranged that each projectile should 

 strike with a work proportional to its diameter. Thus, suppose 

 the comparison to be made between a 7-inch shot animated with 

 a " work" represented by 1,000, and a 9-inch projectile, the latter 

 should strike with a " work " reijresented by 1,286, or in the pro- 

 portion of 9 to 7. Having finished the details of these exper- 

 iments. Captain Noble jsroceeded to consider the effects of shot 

 striking a plate obliquely or at an angle. A small number of 

 experiments have lately been made in connection with this part 

 of the subject, and, although further trials are necessary, the 

 general results go to prove that the power of perforation pos- 

 sessed by the shot is diminished in the proportion of the sine of 

 the angle of incidence to unity. 



The subject of cast-iron jirojectiles next claimed attention, and 

 Captain Noble explained the difference between the effects of 

 cast-iron and steel shot. With the former, much of the total 

 "work" is expended in breaking uj^ the projectile on striking, 

 and hurling the pieces in different directions, whereas, when the 

 shot'are carefully manufactured of the very best steel, very little 

 "work" is done on the projectile, and, in some instances, the 

 material of the shot has been so perfect, that its altei-ation of form 

 after penetrating the plate has been almost inappreciable. 



From this subject Captain Noble j^assed to the consideration of 

 the proper form and material of projectiles to be used for the 

 penetration of iron-clad defences. It has been clearly demon- 

 strated by numerous experiments, that ordinary cast-iron is 

 almost useless as a material for the manufacture of the above 

 projectiles. Steel is an excellent material for shot, but it is also 

 most expensive ; and, as recent experiments have shown that Pal- 

 liser's chilled iron is almost, if not quite, as good as steel, we 

 shall probably use this material for solid shot, and employ steel 

 for shells alone. Various forms of head have been proposed for 

 steel projectiles. Thus, we have had the flat head, relied on by 

 Mr. Whitworth, the round head, elliptical head, etc. The flat 

 head has gained a great reputation, from being the shape used by 

 Mr, Whitworth in his first experiments against the "Warrior" tar- 

 get. Of all these forms, however. Captain Noble prefers the 

 pointed, or ogival head; and he described, by means of a dia- 

 gram, the difference in effect between the pointed and the blunt 

 form. The blunt, that is, flat-headed or round-headed shot on 

 striking an iron-clad structui-e, such, for instance, as the "War- 

 rior," punches a piece of armor out of the plate, and drives it into 



