510 THE RAKER METALS AND THEIR ALLOYS. 



shot with which Colonel Palliser's name is identified proved to be for- 

 midable and effective. The point of such a projectile was sufficiently 

 hard to retain its form under impact with the plate, and it was only- 

 necessary to impart a modern velocity to a shot to enable it to pass 

 through the wrought-iron armor (A, fig. 1, PL XXVI). 



It soon became evident that, in order to resist the attack of such pro- 

 jectiles with a plate of any reasonable thickness, it would be necessary 

 to make the plate harder, so that the point of the projectile should be 

 damaged at the moment of first contact, and the reaction to the blow 

 distributed over a considerable area of the plate. This object should 

 be attained by either using a steel plate in a more or less hardened con- 

 dition, or by employing a plate with a very hard face of steel and a 

 less hard but tougher back. The authorities in this country during the 

 decade 1880-90, had a very high opinion of plates that resisted attack 

 without the development of through cracks, and this led to the produc- 

 tion of the compound plate. The backs of these plates (B, fig. 1, PI. 

 XXVI) are of wrought iron, the fronts are of a more or less hard variety 

 of steel, either cast on or welded on by a layer of steel of an interme- 

 diate quality, cast between the two plates. Armor plates of this kind 

 differ in detail, but the principle of their construction is now generally 

 accepted as correct. 



Such plates shown by the Plate B resisted the attack of large Pal- 

 iiser shells admirably, as when such shells struck the plate they were 

 damaged at their points, and the remainder of the shell was unable to 

 perforate the armor against which it was directed. An increase in the 

 size of the projectiles led, however, to a decrease in the resisting power 

 of the plates, portions of the hard face of which would, at times, be 

 detached in flakes from the junction of the steel and the iron. An 

 increase in the toughness of the projectiles by a substitution of forged 

 chrome steel for chilled iron (see lower part of Plate B) secured a vic- 

 tory for the shot, which was then enabled to impart its energy to the 

 plate faster than the surface of the plate itself could transmit the 

 energy to the back. The result was that the plate was overcome, as it 

 were, piecemeal; the steel surface was not sufficient to resist the blow 

 itself and was shattered, leaving the projectile an easy victory over the 

 soft back. The lower part of Plate B (in fig. 1, PI. XXVI) represents 

 a similar plate to that used in the Xettle trials of 1888. 1 It must not 

 be forgotten, in this connection, that the armor of a ship is but Ifttle 

 likely to be struck twice by heavy projectiles in the same place, 

 although it might be by smaller ones. 



Plates made entirely of steel, on the other hand, were found, prior to 

 1888, to have a considerable tendency to break up completely when 

 struck by the shot. It was not possible, on that account, to make their 

 faces as hard as those of compound plates; but while they did not 

 resist the Palliser shot nearly as well as the rival compound plate, they 



1 Proceedings Institution Civil Engineers, 1889, Vol. XCVIII, p.igo 1-et seq. 



