SIX WILLIAM SIEMENS, F.R.S. 413 



s|-;ik ; whereas in steel, although there was a greater total 

 si i. ii-th, the material must not be strained to an undue degree at 

 any one point. To make his meaning clear, la- iui<;ht be permitted 

 i<- tk'scribe an experiment which he had occasion to make some 

 time ai:o, with the view of constructing a link for a large brid^-. 

 The first idea was to rivet two bars together in the way usually 

 adopted. In tying two steel bars riveted together in the way 

 represented, both bars being tapered breadthways to a point, and 

 the rivets forming a diamond shape, he found that the breaking 

 strain across the joint was, as Mr. Bender had described, about 

 per cent, only of the strain which the net area ought to give. 

 But what was the result of the experiment ? The steel did not 

 break across the full section of the united bars, or across the 

 section of the greatest number of holes, but in bringing on the 

 strain to the bar, the first rivet and the last rivet would receive 

 nearly the whole strain. The material itself, being highly elastic, 

 acted as one body in the middle, and the elastic strain was thrown 

 to the end rivet on either side. The end rivet generally gave way 

 with shearing. The two rivet-holes that followed had sufficient 

 resistance to commence what might be called a tearing action 

 through the solid bars, and the total resistance was certainly very 

 much below what it should have been. Another result which 

 came before him in connection with Lloyd's surveys, was this : 

 A test-bar was riveted to a strong pair of tongs ; and, to the 

 surprise of the gentleman who made the test, the bar, instead of 

 giving way at the point of least section, gave way at the foremost 

 bolts attaching the bar to the tongs, again showing that the two 

 rivets receiving the strain in the first instance, set up a tearing 

 action, which made the line of breakage about three times the 

 length of the line of least section. In all steel structures that 

 ought to be borne in mind. Bars should never be joined by simple 

 riveting ; they should be dovetailed together in such a manner 

 that no tearing action could be set up. He believed, when 

 engineers had mastered the art of constructing with steel, it 

 would be found to be a thoroughly reliable material. 



