404 THE SCIENTIFIC PAPERS OF 



the strain upon the inner tube ; and if it was able to resist the 

 crushing pressure in the first instance, the heating of the inner 

 tube would greatly augment the strain. He thought that was the 

 reason why men like Sir William Armstrong and the Woolwich 

 authorities, who well knew what they were about, had not 

 ventured to give that distribution of strain by shrinkage which 

 mathematical reasoning would lead them to adopt. The author 

 would probably admit that the mathematical knowledge which he 

 brought forward nineteen years ago would not have remained idle 

 for so long a time if it could have been advantageously applied ; 

 but Dr. Siemens was clearly of opinion that in the construction of 

 the Woolwich guns it was impossible to apply that reasoning 

 properly. But the author did not really intend to make a gun 

 by shrinking on iron rings upon a steel core ; he had brought 

 forward a construction of his own, which had something very 

 pleasing to recommend it at first sight. He took a lining tube, 

 and bound upon it several layers of wire, increasing and varying 

 the strain of the wire in such a way that when the inner pres- 

 sure the maximum powder pressure was applied, each portion 

 of the material bore the same amount of tensile strain. There 

 again, however, the author had not contemplated, or, at all 

 events, had not brought forward, the result of the crushing action 

 of that amount of binding force upon a comparatively small tube. 

 The tube was made of cast-iron, which resisted compression better 

 than extension, and to that extent the construction might be very 

 proper ; but the powder pressure in heating the tube would, he 

 apprehended, work a change in the tensions, the same as it would 

 do in the iron coils, either causing the wires to be overstrained, or 

 the tube to be crushed under that strain. The question was, 

 however, whether it would be possible to put the material into 

 any more satisfactory form. When the powder pressure acted, 

 artillerists would like to distribute the force uniformly over the 

 material ; but they had to contend with the different portions 

 under the two conditions of rest and of action from within. One 

 great drawback to the author's proposed system, which he himself 

 admitted, was that he had a resistance against bursting strain 

 without resistance in the longitudinal direction. The author 

 remedied that by putting a very heavy mass into the breech piece 

 of the gun, connecting that heavy mass with a protecting tube 



