58 
MR. H. TOMLINSON ON THE INFLUENCE OF STRESS 
though the values given in the last column of Table II. are in consequence of the want 
of knowledge of cr approximate to the true ones, they must be sufficiently so to 
prove that not only is the total resistance of the carbon increased by loading but so 
also is the specific resistance. 
The mean value of the specific resistance of the different specimens is 4193 X 10 -6 , and 
is therefore more than 100 times greater that the corresponding number for platinum- 
silver, which latter metal ranks highest in the list of metals in Table I. 
Nickel. 
Through the kindness of Messrs. Johnson and Matthey, who after some difficulty 
succeeded in drawing for me two pieces of almost pure nickel wire 8 feet in length, I 
was able to make some experiments on this metal, in which I obtained results so 
completely differing from those observed in the case of the other substances, that I 
may perhaps be excused for treating them in some detail. 
Fig. 10. 
The metal when first received was in the hard drawn condition, and in this state was 
tested for torsional rigidity and longitudinal elasticity, for the former in the usual 
manner and for the latter by longitudinal vibrations. The pieces were then suspended 
in the air chamber, and since it was not thought desirable to bend the wire, the 
following arrangements were made, which are sufficiently shown in fig. 10. 
