558 British Association for the Advancement of Science. 



Relative strength of hot and cold blast iron to resist a transverse 

 strain at different degrees of temperature. 

 Cold blast 949-6 at 32°. Hot ditto 919-7, Mean. 

 Ratio of strength, 1,000 : 977*6. 

 Power to resist impact, 1,000 : 1,039. 

 Cold blast 7481 at 191°. Hot ditto 823-6. 

 In these experiments it appeared that the cold blast lost in strength 

 from 32° up to a blood-red perceptible in the dark, as 949'6 to 723'1 ; 

 whereas in the hot blast the strength is not so much impaired, being 

 as 917*7 at the freezing point, and 8297 when perceptibly red in the 

 dark. 



In all former experiments on the transverse strain of cast iron it has 

 been assumed, that the elasticity remained perfect up to one-third the 

 breaking weight. In pursuing these experiments, discrepancies were 

 noticed, and results widely different to those generally received were 

 observed. It was found that one-seventh, and in some cases, one- 

 eighth the breaking weight was sufficient to produce a permanent set. 

 These facts induced an extended series of experiments, principally to 

 determine what load was necessary to effect a permanent set ; and, 

 if such weight, continued for an indefinite time, would break the bar. 

 It became a question of great importance to know, if a weight having 

 once impaired the elasticity, would or would not, if continued, increase 

 the deflection. The inquiry therefore, was — To what extent can cast 

 iron be loaded without endangering its security ? To solve this question 

 ten bars of hot and cold blast, differently loaded, were placed upon a 

 frame, to ascertain the amount of deflection at stated periods, and to 

 determine what was necessary to break the bars with their respective 

 loads. 



Inches. 

 In the cold blast, with a load of 280 lbs., the de- 

 flexion increased in 103 days from 1*025 to 1*033 



Hot blast, ditto from 1-173 to 1-197 



Coldblast,withaload of 336 lbs., increased in 105 



days from 1-344 to 1-366 



Hot ditto, from 1-573 to 1627 



Cold, with a load of 392 lbs., increased the deflec- 

 tion 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 deflection 

 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, 4481b. 



Mr. Fairbairne stated, that all the irons were made of the same ma- 

 terials, and under the same circumstances. The irons were of fifty 

 6orts. 



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 lbs. to the foot. Mr. Fairbairne stated 

 that some of the loads were more, some less, and that a weight of 280 



