420 



Mr. R. C. Nichols on the Resistances 



centre of the bars submitted to transverse strain may have 

 been equal to the greatest tensile stress supported without 

 rupture in any of the bars subjected to direct strain, which 

 was 21,745 lb. 



When the maximum tensile stress is first nearly approached 

 the tensile stress at the lower fibres will be somewhat less than 

 that given by the equation, but may be assumed to be deter- 

 mined by it until it is equal to a maximum somewhat below 

 the breaking stress, and afterwards to remain constant at the 

 same amount. If it had continued to vary with the load its 

 amount would be that given in column 5, and the actual 

 maximum tensile stress may be taken to be that in column 6. 



Column 7 gives the ratio r of the two last values when the 

 former exceeds the latter, and the quantities in the remaining 

 columns are calculated by the equations above deduced from 

 the theory of overstrain. 



The annexed diagram (fig. 11) exhibits in a more striking 

 form than the Table the relative proportion of the calculated 

 deflexions to those measured and of both to the normal de- 

 flexion. The lengths of deflexion in the diagram are three 

 times the actual amount. 



It will be seen that in every instance except one, where 

 there is obviously an error in the measured deflexion, the cal- 

 culated amounts of deflexion are less than those observed. It 



