4IO -THE SCIENTIFIC PAPERS OF 



edge would throw a corresponding tensile strain upon the metal inside 

 the line of rivet holes. The result was, that if in any of these 

 holes there was the slightest defect or the slightest discontinuity of 

 the even surface a tear would begin. It was said that metal which 

 ought to stretch 25 per cent, before breaking should not have torn 

 under these circumstances, because they could find that it had not 

 stretched at all. But, in arguing this point, gentlemen forget the 

 fact that in tearing a material they did not extend it. A tear 

 meant applying the whole of the force available upon absolutely 

 one point of the metal. At that one point the metal might 

 be capable of stretching even 50 per cent., but this would 

 not save it, inasmuch as the force was confined to one 

 point. At that point it would tear, and afterwards at another 

 point, and so on. All the mysterious failures reported might in 

 nearly all cases be attributed to tearing action, which was gene- 

 rally set up at rivet holes if the rivets at those holes took more than 

 their due proportion of the strain. He knew of another instance 

 where failure took place in a testing bar. It was not intended to 

 test the strength of a riveted joint. In fastening the piece it was 

 held by two large rivets on each side, followed up by smaller rivets. 

 With a metal of high elasticity, such as mild steel, a great strain 

 would be thrown upon the part most forward. The supports, 

 which were backward, could not come into full bearing condition 

 till the forward part had taken the proper strain. Wherever that 

 strain exceeded certain limits, tearing action would take place 

 from any part where the continuity was broken. One of the chief 

 advantages of drilling over punching was that the drilling made a 

 smoother hole, and there was less susceptibility to tearing; but, 

 as stated by Mr. Barnaby, mild steel should not require either the 

 particular attention or expense due to drilling, nor should it 

 require annealing. The failures spoken of were generally at- 

 tributable to some fault in the treatment. He would rather not 

 touch upon the subject of a comparison between Bessemer metal 

 and the metal with which his name was connected. He had more 

 than once expressed his great admiration of the Bessemer process, 

 and of the excellence of the metal which could be produced by it. 

 At the same time it was not probable that he should have gone to 

 the great labour and expense of developing another process if he 

 had not thought it possessed some particular merits. It would 



