Mr. Fairbairne on Hot and Cold Blast Cast Iron. 557 



being constant. In comparing two irons, the greatest care was taken 

 to subject them as nearly as possible to the same treatment. 



A series of experiments was also made to determine the strength 

 of hot and cold blast iron at various temperatures, from 32° (the free- 

 zing point) to the boiling point ; for this purpose a cast-iron trough 

 was employed, in which the bars to be broken were placed and covered 

 with snow or water (which was kept at the proper temperature by a jet 

 of steam) as the case required ; the weights were then gradually laid 

 on until fracture took place. 



The strength of bars made red hot was also tried, and contrary to 

 expectation, they retained their tenacity and power to resist the load 

 to a considerable extent : the reduction of strength in a bar one inch 

 square, in a range of temperature from 32° to that of redness was ra- 

 ther more than one-sixth, the deflection being upwards of l£ inch in a 

 bar 2 feet 3 inches long. 



RESULTS. 



Carron iron, No. 2. (Scotch.) 

 Mean ratio of transverse strength, assuming the cold 



blast iron at 1000 : 9799 



Mean ratio of power to resist impact . . . 1000 : 1038*9 



Whence in the transverse strength of Carron iron No. 2, using a 

 variety of forms of section, the strength of the cold blast is to that of 

 the hot blast, as 100 to 98, nearly. 



Devon iron, No. 3. 

 Mean ratio of strength in sections of various forms (thir- 

 teen experiments) 1000 : 1409 



Power to sustain impact 1 000 : 2742 



This is an exceedingly hard iron with a singular appearance, the cen- 

 tre or more granulated parts of the fracture being surrounded with a 

 circle having the appearance of hardened steel. 



Buffery, No. 1, Staffordshire iron, cold and hot blast. 



Mean ratio of breaking weight 1000 : 925 



Mean ratio of power to resist impact 1000 : 965 



In the buffery iron, the hot blast manufacture is weaker whether we 

 view it in its transverse strength, or its power to resist impact. 

 Coed Talon, No. 2, North Welsh iron. 



Mean ratio of strength in a number of experiments 1000 : 1014 



Mean ratio of power to resist impact 1000 : 1219 



Modulus of elasticity in lbs. for a bar of one inch square. 



Cold blast | Jg^ooo } l 4 >313,500lbs. 



Hot blast {j^g}l4,322,5001bs. 



Elsecar cold blast, No. 1, against Melton hot blast, No. 1, 

 (Yorkshire iron.) 



Mean ratio of strength . . 1000 : 809 



Mean ratio of power to resist impact 1000 : 858 



The modulus of elasticity in all the irons are computed j but only 

 given in a few cases in the results. 



