37 8 ARMOUR-PLATE 



with a layer of copper between, in a mixture of carbon, brown sugar and water of the 

 consistency of compressed snow, and the whole mass is heated to a temperature of 2,000 

 F., when the copper melts away into the adjacent steel, forming a perfect weld. The 

 advantage to be gained by such a process is obvious. One of the limitations of the 

 cementation process is that the carbon, upon which the hardness of the face mainly 

 depends, only penetrates to a depth of about one inch and, consequently, there is a 

 difficulty, in the thicker plates, of getting the best relation of thickness between hard 

 face and tough back. By the Simpson process if successful it would be possible to 

 obtain any desired relation between the two and to use any class of steel which might 

 be preferred. Further it would appear possible to employ one or more intermediate 

 layers, if it should be found desirable, to prevent too abrupt a change in the character of 

 the steel. The possibilities of the process depend upon the soundness of the weld the 

 point in which the earlier compound plates failed. 



An interesting account of the Krupp process as carried out at Essen was given in Engi- 

 neering of August 16, 1912. It is noteworthy as giving the approximate temperatures of the 

 various stages, including the differential heat. The account differs in some details from 

 earlier descriptions, notably in the use of illuminating gas instead of solid carbon in the 

 cementation process and in the method of the final chill. 



Modifications in Thickness etc., of Plates. The increased power of the attack, which, 

 apart from the tendency to adopt heavier primary guns, is due partly to improvements 

 in the projectile and cap, considered merely as perforating or punching tools, and partly 

 to increased ranging power due to the elongated form of head now universally adopted, 

 is having the inevitable effect, in the absence of any revolutionary change in the character 

 of plates, of increasing the maximum thickness of the main armour; and it has been stat- 

 ed that in the U.S. battleship " Nevada " the maximum belt thickness is to be 13! 

 inches as against the n inches of the " Wyoming," and her foreign contemporaries, 

 while 1 armour of as much as 18 inches thick is to be used on the port plates of the 3-gun 

 turrets. During 1911 trials are known to have been carried out in the United States 

 with 1 8-inch plates. On the other hand there would appear to be a tendency in America 

 to drop light vertical armour for the protection of the secondary armament on the 

 ground that it merely serves as an effective shell burster. In the latest British 

 battleships it is reported that light armour for the secondary guns is reverted to. 



Another modern feature of interest is the use of plates of varying thickness vertically, 

 for belt armour. There is thus no marked line of cleavage, as formerly, between the 

 thicker and thinner horizontal layers of the belt. 



The use of cast steel such as Hadfield's " Era " steel for gun shields, armoured 

 tubes etc., is increasing. Its resisting value is high, a recent example of a 2.7-inch plate 

 showing a figure of merit well over 2 against capped 4-inch armour-piercing shell. 



This class of material is specially adapted to cases where a monolithic form is desir- 

 able, and enables the thickness to be graduated in the most economical way to suit the 

 exposure of the various faces to attack. 



In connection with the penetration of armour, a point of considerable interest, whether, 

 as is usually held, the projectile remains sensibly at a tangent to the trajectory during flight, 

 or whether, as has been occasionally maintained by certain ballistic heretics, it remains 

 parallel to the initial direction of projection, has recently been discussed (see Scientific 

 American, August 10 and 17, 1912) by Adnural Twining, who shows both theoretically and 

 from actual firing trials at long ranges against armour that the orthodox theory is correct. 

 The importance of the point is obvious when we consider that no projectile could withstand 

 the cross breaking strain to which it would be subjected on impact, at any but very close 

 ranges, if it retained its original direction, so that the employment of projectiles specially 

 designed to perforate armour would be a sheer waste of money. 



Caps. Complete agreement as to the exact way in which the cap assists penetration 

 has not yet been arrived at. All authorities concur in attributing great importance to 

 the lateral support which it affords to the point on impact above a certain velocity, 

 which varies in all probability with the particular plate and projectile involved (there is 

 a general agreement that the minimum velocity to render the cap effective varies from 

 about i, 600 to i, 800 f.s.); but while some, following Tresidder (see the latter's lecture, 



