WILLIAM SIEAfENS, P.R.S. 



423 



results \\vre much && might have been expected. The author had 

 dealt with various metals at the limits of 5 and AO" Fahr. The 

 limit was a narrow one, and it could not be expected that the re- 

 sults of the experiments could be such as would lead to a general 

 ri inclusion regarding the effect of temperature within wider limits 

 (in materials of that description. There could be no doubt that 

 toU-rably pun; material must be stronger at the lower temperature 

 than at the higher, because the last particles of the material were 

 closer in contact at the lower than at the higher temperature. For 

 a similar reason the material would resist a blow rather less at the 

 lower temperature than at the higher. But he agreed with the 

 observations of previous speakers that no influence was produced 

 by those degrees of temperature on the absolute structure of the 

 metal. It was quite out of the question to expect to change the 

 metal from a crystalline to a fibrous condition, and back again 

 from a fibrous to a crystalline condition, by lowering or raising 

 the temperature a few degrees. The paper, though valuable of its 

 kind, was suggestive chiefly of what had been omitted to be taken 

 into consideration ; for instance, the author had not in the first 

 instance given a chemical analysis of any of the materials he had 

 employed, though that omission had, he believed, since been reme- 

 died ; but at any rate he had drawn no conclusion from such 

 analysis. Nor had he considered the elastic limit of the materials, 

 although to an engineer the elastic limit and the condition of the 

 material up to the elastic limit were more important than the 

 breaking strain. Engineers did not want to break down with 

 their materials ; but they wanted to see to what extent it was safe 

 to use them. It would have been most interesting if the author 

 had given the elongation due to the rate of elastic extension at 

 different temperatures. It was Mr. Barlow, the President, who 

 first established by experiments that steel of various tempers was 

 equally strong up to a certain limit. In other words, that if a bar 

 of very mild steel having a sectional area of 1 square inch pure 

 iron, as Mr. Adamson had correctly described it, was weighted 

 with a ton weight, the same absolute extension would ensue as in 

 weighting a bar of very hard steel of 1-inch sectional area and of 

 the same length, and so on, each ton additional weight producing 

 the same amount of extension in both bars until the elastic limit 

 of the mild metal was reached. These results, which he must 



