256 Professor John Oliver Arnold [Feb. 23, 



slightly beyond the elastic limit, the steel registered tests varying 

 from 230 to 1292 alternations. The most disconcerting feature in 

 these astoundingly divergent tests was that the test bars registering 

 them were identical in micrographic structure. 



At the Cambridge meeting of the British Association, the lecturer 

 suggested that these divergent tests must be associated with opposite 

 sides of the plate subjected to varying heat treatment. The lecturer 

 was quite wrong ; and, after twenty-five years experience, had failed 

 to realise the fact that in connection with steel, one must often expect 

 the unexpected. 



Remarkable failures in structural steel were commonly associated 

 with the phenomenon called " fatigue." What was " fatigue " ? 

 Some little time ago in an important naval trial at the King's 

 Bench, Counsel requested the lecturer to define for My Lord the 

 meaning of this term, which had frequently occurred during the trial, 

 and which he failed to understand. Unfortunately the lecturer also 

 was involved in the outer darkness of My Lord on this matter, but 

 was compelled to give " fatigue " at that time a definition, which 

 remains substantially true today, namely, that he regarded " fatigue " 

 as a generic term used to clearly explain all cases of fracture which 

 were not understood. Before venturing to suggest an explanation 

 for these mysterious fractures for which popular blame often fell upon 

 men who were doing their very best, he would ask his hearers to 

 imagine that that small cloud, no bigger than a man's hand, now 

 hovering over the North Sea, should burst in storm, and that our 

 armour, our guns, and our armour-piercing shells, should be put to 

 the stern implacable test of actual warfare. Supposing our guns 

 were faulty, our shells failed to penetrate the armour of the enemy, our 

 armour was incapable of protecting the gallant inmates of our battle- 

 ships ; assuming this hypothesis, which the lecturer believed to be 

 totally untrue, what would all this mean ? It would mean that the 

 internal architecture of British wrought steel was all wrong, and the 

 interesting question thus arose, who were the men responsible for the 

 internal architecture of these metals ? The lecturer knew them well. 

 They were grave-eyed men with set mouths, who week after week, 

 month after month, and year after year, lived and moved, and had 

 their being, and sometimes died, amid the flare of gigantic furnaces, 

 and the rattle of Titanic rolls, steadfastly working upon those metals 

 which formed Britain's first line of defence, and to-night on behalf of 

 these inarticulate men, the lecturer confidently asked his distinguished 

 audience to exclaim in their hearts " These men have deserved well of 

 their country." 



Reverting to the i-emarkable and disconcerting fact that two pieces 

 of the faulty boiler-plate steel of identical structure so far as could be 

 seen by the microscope, gave astoundingly different results under 

 dynamic stresses, the lecturer put forward as a tentative hypothesis 

 the theory that, underlying the gross and visible micro-structure of 

 the steel there existed a molecular structure, which in the present 



