416 



REPORT — 1856. 



Table XVIII.— Sectional area =-24.850. 



There is a slight diminution in the strength of this bar as compared with 

 the previous experiment at —30°, but the discrepancy is scarcely appreciable, 

 and may easily be accounted for by inequalities in the forging or rolling of 

 the bar. 



Table XIX.— Sectional area =-24850. 



The strength of the bar in this experiment is a trifle in excess of those 

 fractured at — 30° and 60°. It would have been rather stronger had it been 

 rounded at the shoulder to prevent its pulling out there, as shown in the figure. 

 However, there is little difference in the strength of the material through 

 a range of 90° of temperature. 



Table XX. — Sectional area =-24850. 



It has already been observed that the whole of the specimens for experi- 

 ment were cut from one bar, and as each experiment was conducted with 

 great care, both in preparing the specimens and laying on the weights, we 

 are bound by the results to believe that the increased strength of this de- 

 scription of iron is due entirely to the increase of temperature. In this ex- 

 periment, it will be seen that the resisting power of the bar ruptured at 1 14° 

 was to that of the bar ruptured at 60° (Table XIX.) as 1 : -898. 



