516 



Scientific Proceedings^ Roj/nl Dublin Society. 



Tlie wires were tested under exactly the same conditions, and were of the 

 same length (226 cms.) and the same diameter (0'163 em.) ; had the same 

 longitudinal load (0'5 x 10^ grammes per sq. cm.), and the current density 

 was the same in each — viz. 100 amperes per sq. cm. Both were made as soft 

 as the nature of the material and method of annealing would permit. The 

 simple rigidity of the iron wire was 774 x 10", and of the nickel wire 

 707 X 10'' grammes per sq. cm. The maximum twist for the iron (40'5 mm.) 

 took place in a longitudinal magnetic field of 2'5 units, and the maximum 

 twist for nickel (95 mm.) in a field of ly units. 



I00» 



50 



/ 



^ 



10 



Miigiieiic Field 11. 

 Fig. 6. — Similar wires of nickel and iron contrasted. 



Summary. 



^N.B. — Some results previously obtained with iron wire are also given here 



for convenience of contrast and reference.] 



1. Soft nickel wire heated to a bright cherry-red heat when loaded at 



the rate of lO'^ grammes per sq. em. has its rigidity increased about 6 per 



cent., and its electrical conductivity decreased 8-8 per cent. 



Soft iron wire when treated in the same way has its rigidity increased 1-8 per cent., 

 and its electrical conductivity decreased 2-1 per cent. 



