510 



Scientific Proceedings, Royal Dublin Society. 



one more lightlj' loaded. This was seen in fig. 1 (p. 504), and is also seen 

 in fig. 4 (p. 509), wliich is the graph of the results obtained with a wire of 

 liardness between Hj and Hf, and of length 181 cms. 



To the right of the figure (over the point representing a magnetic field of 

 50 units) the top curve is obtained with a load on the wire of 3 x 10* grammes 

 per sq. cm., the lowest curve being that obtained with a load of 0"5 x 10* 

 grammes per sq. cm., and the middle curve that obtained with the medium 

 load of 1"5 X 10* grammes per sq. cm. It was thought possible that these 

 curves might re-cross if higher longitudinal magnetic fields were applied to 

 the wire under the three separate loads ; a test was therefore made in whicli 

 longitudinal magnetic fields up to a maximum of 200 units were applied ; 

 and the results are given in Table IV, which shows that the curves maintain 

 their relative positions even in that high field, and the slope of the curves, 

 when the results were plotted, show that they are not likely to re-cross for 

 even higher fields.' 



Table IV. 



In some previous work* with iron wires it was found that the longitudinal 

 magnetic field in which the maximum twist occurred was directly propor- 

 tional to the current density in the wire, and tests were made to find out if 

 nickel wire obeyed the same law. 



1 The long solenoid at present in use for these experiments could not conveniently carry a current 

 to give magnetic fields higher than 200 units. A new solenoid, however, is being wound, by means 

 of which wires 1 metre long can he tested in mucli higher fields. 



-Scient. Proc. Roy. Dub. Soc, vol. xii., p. 493. 



