156 Wisconsin Academy of Sciences, Arts, and Letters. 



Fairbairn, who made tests a little beyond the elastic limits, re 

 moved and reapplied the same weight a number of times, and 

 ultimately produced fracture with a strain much less than that 

 which would have done so if the first strain had been carefully 

 and gradually increased. 



From a common sense point of view alone, it would appear 

 as though a bar of iron of uniform section would be perma- 

 nently injured by a breaking strain, since at the moment of 

 rupture the particles would be all uniformly strained and rup- 

 tured until the break occurred at some point of mechanical or 

 other imperfection, the remaining portions would remain in 

 their almost entirely ruptured condition. In my experiments 

 on timber I found that the strain which produced a permanent 

 pet would break the same, and that a less weight applied for 

 a longer time would also produce rupture if the specimen had 

 been injured previously. 



The heat evolved by tearing asunder a bar of iron is com- 

 mon to violence, and is the result of friction produced by the 

 excursion of the molecules, simply denoting work done. The 

 almost entire absence of heat in the subsequent fractures in 

 the aforementioned experiments would go to show that the 

 wcrk had already been done. I have purposely dwelt upon 

 this subject to invite inquiry, and have based my arguments 

 not upon my own, but upon the knowledge of men who have 

 been the leaders of special branches of science and industry. 

 Another case more serious than the former frequently makes 

 its appearance in lengthy articles ; it is the effect of frost upon 

 the strength of iron and steel. The subject is a comparative- 

 ly new one, and has but very recently been seriously consid- 

 ered by scientific men. 



Railway companies have been in the habit of attributing 

 every accident in winter by broken rails or axles to the effect 

 of the frost upon the metal. In some manner this led to 

 investigations, and several have appeared who have attempted 

 to refute the idea entirely, and who endeavor to prove that 



