ARMOUR-PLATE 377 



trajectory was ensured. Experiments were then carried out with gun projectiles in 

 order to obtain similar advantages, and it was found that the remaining velocity increased 

 with the radius of the head, but that the accuracy became less if the point was unduly 

 acute. A radius of head of about 4 calibres was finally decided upon as giving the ad- 

 vantage of increased remaining velocity, or longer range with good accuracy. 



The perforating power of the armour piercing projectile has been much increased by 

 the introduction of the cap. The cap as first introduced was solid with a flat nose of 

 considerable thickness in front of the actual point of the shell. Lately this thickness 

 has been greatly reduced, but in order to preserve the external form of the large radius 

 ogive the cap is provided with a hollow point. 



By the use of a higher grade .of steel, the thickness of the walls of armour piercing 

 shell can be slightly reduced; thus the internal capacity of the projectile is increased 

 and a larger bursting charge of high explosive can. be used. 



The high explosive bursting charge for the various kinds of projectiles has also in- 

 creased in weight, so that modern shells are more powerful than those of older types. 

 In these a bursting charge of lyddite, i.e. melted picric acid, was employed. This mate- 

 rial, although a most powerful explosive, has certain drawbacks, of which the following 

 may be mentioned: it requires a somewhat high temperature to melt it for the purpose 

 of running, it into the shells, and it readily forms dangerous combinations with certain 

 metallic salts should these be present; great care has therefore to be observed to prevent 

 any possibility of their presence. An alternative chemical substance " trinitrotoluol" 

 has come into favour; this melts at a very much lower temperature, and has the further 

 advantage of not forming dangerous. compounds as picric acid does. On the other 

 hand, it is more inert, so that a powerful exploder is required to properly detonate it ; but 

 this inertness is otherwise an advantage in as much as it enables an armour piercing 

 shell filled with trinitrotoluol to perforate armour, even at a striking velocity of over 

 2,000 f.s., without exploding the shell. Thus, with a well designed fuze and exploder, it is 

 possible to burst the shell after it has passed through the armour into the interior of 

 the ship. (A. G. HADCOCK.) 



V. ARMOUR-PLATE 1 



Progress of Manufacture. Improvements in armour-plate manufacture, with a view 

 to increasing the resisting power of plates, are the jealously guarded secrets of the manu- 

 facturers and their respective Governments, As far as can be ascertained, however, 

 there have been no further developments during the last two or three years comparable 

 in importance with those introduced in the past by Harvey or Krupp. Minor improve- 

 ments have no doubt been made, and the actual quality of an average plate is probably 

 better than it was three or four years ago; but, relative to the attack, it is doubtful 

 whether any progress has been made in the resisting power of armour. 



It is claimed, however, that in the United States, at least, a considerable advance 

 has been made in the case of the thinner plates, up to 3 or 4 inches in thickness, including 

 those used for decks, splinter-proofs, roofs of turrets, conning towers, etc., by the adop- 

 tion of a nickel-chrome-vanadium steel subjected to a special heat treatment. In view 

 of the possibilities of aerial attack, the importance of horizontal armour, especially in 

 the form of light over-head cover, is greater than ever, and for this reason alone any 

 development in the resisting power of thin plates is to be welcomed. In the case of the 

 thicker plates no definite advance of any importance has been reported, except in the 

 matter of surface flaking when struck, which is said by Rear Admiral N.C. Twining, the 

 Chief of the United States Bureau of Ordnance, to have been very greatly reduced in 

 recent years (see Scientific American, December 9, 1911). 



In the above remarks, no account has been taken of the Simpson process, which 

 would seem to be still in the experimental stage. The process is one of welding together 

 steel plates of varying hardness by means of copper. As described in the Times (Lon- 

 don) of March 29, 1911, the weld is effected as follows. The plates to be united are placed, 



1 See E. B. ii, 578 et seq. 



