British Association for the Advancement of Science. 295 
Hot blast, ditto, from - - - - 1,173 to 1,197 
Cold blast, with a load of 336 lbs., increased in 105 
- days, from - - - - - - 1,344 to 1,366 
Hot, ditto, from - - - - 1,573 to 1,627 
Cold, with a load of 392 lbs., et the deflection 
in 108 days, from - - - - - 1,786 to 1,843 
Hot, ditto, from - - - - - 1,891 to 1,966 - 
Cold blast, with a load of 448 lbs., continued to increase in deflec- 
tion, and ultimately broke, after sustaining the weight 35 days. All 
the bars from the hot blast broke in the act of loading them with the 
above weight, 448 lbs. 
Mr. Fairburn stated, that all the irons were made of the same 
materials, and under the same circumstances. ‘The irons were of 
fifty sorts. : 
Mr. Cottam inquired as to the elastic forces. Dr. Young and 
Mr. Tredgold had found that the strength of the material would fail 
if loaded beyond its elastic force ; he wished to know whether the 
loads had been more or less than 850 Ibs. to the foot. Mr. Fairburn 
stated that some of the loads were more, some less, and that a weight 
of 280 lbs. produced a permanent set of an inch square bar. The 
President remarked, that the calculation as to elastic forces was 
scarcely to be confided in. Mr. Fairburn, in answer to another 
question, stated, that the hot blast iron was the more flexible and 
better capable of bearing impact; but that all the results of impact 
had been taken from calculations founded on cold blast iron. Mr. 
Fairburn stated, that the crystalline appearance was finer in hot than 
in cold blast. ‘There were no experiments made on the loss by re- 
melting, and none on wrought iron,—all on cast iron. In reply to 
Mr. Cottam, he mentioned, that all the Scotch irons had no cinder ; 
the composition of the others they did not know. Great difficulty 
had been experienced on this point, because the different manufac- 
turers were unwilling to give information.—Mr. Guest professed on 
his part the fullest readiness.—Some conversation took place with 
regard to the peculiarity of appearance in the broken bars. The 
President remarked, that when a rectangular bar of any substance is 
exposed either to fracture, or even to temporary deflection, a similar 
appearance was found: this was known from the experiments on 
glass by polarized light. Mr. Fairburn in assent said the crystals 
were always more compact in the edge than in the centre. Mr. 
Webster inquired whether the elastic weight was always less than 
