S/K WILLIAM SIEMENS, F.R.S. 401 



which lias lately been sent me from America for testing pieces of 

 steel or iron, and after the meeting is closed I will break a test bar 

 of mild steel, that the members may see the amount of elongation 

 of which such a bar is capable before breaking. 



Dit. SIKMEVS. With regard to an observation made by General 

 Younghusband, I should ask permission to say one word. I do 

 not wish to suggest for a moment that a gun, such as is now 

 turned out at Woolwich, is not a very excellent mechanical pro- 

 duction ; and at tha time the materials that were to be used were 

 de3ided upon, thos3 were ths very bast materials that could be 

 obtained. And with regard to iron, I admit the value of putting 

 the strain in the direction of the fibre, but at the present time we 

 have made a very considerable step forward, which I think should 

 be taken advantage of in the construction of guns. If the coil 

 is limited in its length, it gives, a? General Younghusband says, 

 no longitudinal strength, and the inner tube becomes a matter of 

 much greater importance than it would necessarily be if the out- 

 side of the gun, instead of being multifarious, was solid. But 

 there seems to be no reason why, if the outside of the gun was of 

 steel, and the elasticity of that mass of steel was properly distri- 

 buted, it should be divided, and not be of a single piece. If that 

 was the case, the inner tube would have only one function to 

 fulfil, that of taking the rifling ; but it is most essential, I con- 

 sider, that it should be as mild as is consistent with its power to 

 resist abrasion, inasmuch as it cannot be true in principle, although 

 it may be perfectly workable, to have the material of which the 

 lining is composed of greater resisting power than the material 

 surrounding this inner tube, upon which the strength of the gun 

 depends. The lining must necessarily be subjected to very con- 

 siderable expansion through the firing itself. One fact I should 

 like to mention, viz., that a shrinkage of 1 in 1,000 produces \\\ 

 to 12 tons of strain to the square inch, and an elongation of 1 in 

 1,000 is produced by heating the material to 130 Fahr. ; there- 

 fore, if a gun is built up by shrinkage, and the inner tube after- 

 wards heated up to 180 Fahr., the amount of fight between the 

 inside metal and the outside must be just double. If the heating 

 should exceed that limit, as it appears to me it would be likely to 

 do, the strain between the inside and the outside must increase in 



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