246 REPORT — 1867. 



It will be observed from tbe above Summary of Results, that in the re- 

 duction of tbe experiments to tbe vahie of u, or work done in producing 

 rupture, some of tbe specimens are as low as 72 when tbe metal is bard and 

 brittle, and as bigb as 6403 (in Exp. 14) wbere tbe specimen is of ductile 

 Bessemer steel. It required tbe utmost precision to determine witb perfect 

 accuracy tbe elongations of tbe barder specimens at tbe potut of rupture ; and 

 altbougb tbe elongationsVere magnified and carefully taken, tbey are uever- 

 tbeless not to be relied upon wbere tbe value of u is under 300. It would 

 bave been more correct to bave taken tbe elongations from bars three or four 

 times tbe length ; but this could not be accomplished from tbe same bars, as 

 m most cases it was next to impossible to bave them reduced to tbe required 

 dimensions without heating tbe bars and drawing them out under the hammer. 

 This process would bave rendered them useless for comparison, which is not 

 the case in tbe present experiments, where the rupture by tension is identical 

 with that by compression, as they were cut from the same bars after having 

 been submitted to a transverse strain. Prom this it will be seen that each 

 bar has undergone without change the three separate tests of tensUe, com- 

 pressive, and transverse strain. 



