328 



Dr. M. Maclean. On the Effects of Strain 



1 1 . The resistances of the drawn copper and manganin wires were 

 compared with the resistances of the corresponding undrawn copper and 

 manganin wires by the fall of potential method, and it was found that 

 the resistances of the drawn wires (for the same length and cross section) 

 were slightly greater* than that of the undrawn wires. In calculating 

 the total resistance in the circuit external to the galvanometer, this 

 increase of resistance in the drawn wire is not taken into account. The 

 circuit consisted of 60 cm. of the undrawn wire, and 60 cm. of the 

 drawn wire, together with the low resistance galvanometer. By 

 multiplying the current per division, given in the table of Section 9, 

 by the total resistance of the circuit, the thermo-electric difference per 

 degree between drawn and undrawn wires is found. The numbers are 

 given in the following table : 



Less than 1 per cent. 



