SfK WILLIAM SIEMENS, F.R.S. 1 71 



over the whole section. This very property of yielding before 

 breaking made it necessary that it should be fastened along the 

 \vlmle line of its section. In the particular fastening referred to, 

 t wi > larger rivets stood forward, and naturally would take nearly the 

 whole of the strain that fell upon the plate. The other four rivets 

 stood back to such an extent that, before they would receive any 

 considerable portion of the strain, the two forward rivets would be 

 loaded to such an extent as to cause a partial yielding of the metal, 

 and, as they were near the edge, tearing action would set in. Now 

 a material, however strong it might be, could be torn without 

 much effort. Thus if a strip of india-rubber were nicked, it tore 

 with little stress ; whereas if there was no nick, it would bear 

 almost any amount of elongation. In like manner the mild steel 

 had to be treated differently from iron ; and experiments like the 

 present gave better information than any learned essays on the 

 subject could possibly supply. When the strips of the same plate 

 were tested in the usual way, they stood the test as well as every 

 other portion of the material supplied. 



The use of iron rivets had been advocated, and was still advo- 

 cated by many, for riveting these mild steel plates together. He 

 could not too strongly protest against that practice. It was 

 utterly against nature to stick together material like this mild 

 steel with another material, iron, which behaved quite differently 

 as to elongation and yielding. Again, when iron rivets were used, 

 the rivet-holes must necessarily be larger than they would need to 

 be for steel rivets ; being larger they would be put a greater 

 distance apart, and the distance practically chosen was the same 

 as was in ordinary use for iron plates of 20 per cent, greater 

 thickness. Thus the thinner plate was held together at points 

 relatively further apart ; and the result was that the metal between 

 hole and hole could not be so securely held as it should be, and 

 tearing action set in. He was very glad to see that Mr. Boyd 

 had resisted the temptation of using iron rivets, and had adopted 

 steel riveting in these boilers. 



He did not quite agree with the author that punching neces- 

 sarily diminished the strength of a steel plate something like 33 

 per cent. No doubt his experiments had been very carefully made, 

 but there was a great difference between punching and punching. 

 His belief was that on punching a cylindrical piece or " burr " out 



