512 THE BARER METALS AND THEIR ALLOYS. 



less harm to the plate and penetrating less, when its velocity was 

 increased beyond a certain value, a result due to a superiority in the 

 power of the face of the plate to transmit energy over that possessed 

 by the projectile, which was itself damaged, when a certain rate was 

 exceeded. At a comparatively low velocity the point of the shot would 

 resist fracture, but the energy of the projectile is not then sufficient to 

 perforate the plate, which would need the attack of a much larger gun 

 firing a projectile at a lower velocity. 



The tendency to-day is to dispense with nickel and to use ordinary 

 steel, "harveyed"; 1 this gives excellent 6-inch plates, but there is 

 some difference of opinion as to whether it is advantageous to omit 

 nickel in the case of very thick plates, and the problem is now being 

 worked out by the method of trial. Probably, too, the harveyed plates 

 will be much improved by judicious forging after the process, as indicated 

 by some recent work done in America. The use of chromium in the 

 plates may lead to interesting results. 



Turn for a moment to the Majestic class of ships, the construction of 

 which we owe to the genuis of Sir William White, to whom I am 

 indebted for a section representing the exact size of the protection 

 afforded to the barbette of the Majestic. [This section was exhibited 

 and is shown as reduced to the diagram, fig. 2, PI. XXVI.] Her armor 

 is of the harveyed steel, which has hitherto proved singularly resisting 

 to chromium projectiles. 



In this section A" represents a 14-inch harveyed steel armor plate, B 

 a 1-inch teak backing, C a lj-inch steel plate, D £-inch steel frames, 

 andE ^-inch steel linings. 



It will, I trust, have been evident that two of the rarer metals, chro- 

 mium in the projectiles and nickel in the armor, are playing a very 

 important part in our national defenses ; and if I ever lecture to you 

 again, it may be possible for me to record similar triumphs for molyb- 

 denum, titanium, vanadium, and others of these still rarer metals. 



Here is another alloy, for which I am indebted to Mr. Hadfield. It 

 is iron alloyed with 25 per cent of nickel, and Hopkinson has shown 

 that its density is permanently reduced by 2 per cent by an exposure 

 to a temperature of — 30° that is, the metal expands at this tempera- 

 ture. 



Supposing, therefore, that a ship of war was built in our climate of 

 ordinary steel and clad with some 3,000 tons of such nickel-steel armor, 

 we are confronted with the extraordinary fact that if such a ship vis- 

 ited the arctic regions it would actually become some 2 feet longer 

 and the shearing which would result from the expansion of the armor 

 by exposure to cold would destroy the ship. Before I leave the ques- 

 tion of the nickel iron alloys let me direct your attention to this triple 

 alloy of iron, nickel, and cobalt in simple atomic proportions. Dr. 

 Oliver Lodge believes that this alloy will be found to possess very 



1 Engineering, Vol. LVII. 1894, pages 405, 530, 595. 



