400 THE SCIENTIFIC PAPERS OF 



In the discussion of the Paper 



ON THE CONSTRUCTION OF ARMOUR TO RESIST 

 SHOT AND SHELL," by Capt. C. 0. BROWNE, R.A., 



DR. C. W. SIEMENS * said he had been present at the experi- 

 ments on board the "Nettle," to which the paper referred ; and 

 the conclusion he had arrived at was that " compound " armour 

 plating, such as Mr. Wilson's, would not give all the results that 

 were expected of it. It stood to reason that if two metals, different 

 in their character and in their rate of expansion, were united, there 

 must be a tension set up between them at the surface of junction. 

 If such a compound body was struck by a shot, the inevitable 

 consequence must be, either that the two metals would separate, 

 or that the weaker metal would be torn to pieces by the stronger. 

 The latter seemed to have been the case in the experiments ; the 

 iron seemed to be almost in a condition of powder wherever the 

 projectile had penetrated into the iron plate. The plate of Sir 

 Joseph Whitworth was on a different principle, and that plate no 

 doubt withstood the action of the shot remarkably well. But he 

 thought Sir Joseph Whitworth had not at that time fully 

 developed his idea ; because the steel plugs there used acted as so 

 many starting points for cracks. These cracks started not only 

 where the shots struck, but also at other points, where it happened 

 that there was a tension existing. It was known that a steel 

 plate which would resist almost any amount of ill-treatment while 

 it remained a continuous whole, would crack or tear wherever the 

 continuity was broken ; hence in dealing with steel any break of 

 continuity ought to be strictly avoided. Sir Joseph Whitworth 

 had since constructed armour plates that had resisted shot ex- 

 ceedingly well ; and in these he had substituted rings of steel 

 carefully tempered and then screwed together, one ring inside the 

 other. By this means he had avoided the tendency to form 

 starting points for cracks. But that construction had the 

 disadvantage of being one which few works except Sir Joseph 



* Excerpt Minutes of Proceedings of the Institution of Mechanical Engineers, 

 1879, pp. 71-73. 



