48 



Scientific Proceedings. Royal Dublin Soctet//. 



Table IX. 



These values in Table IX lead to a very interesting result, for if we plot 

 the values of the rigidity of the wire as abscissae, and as ordinates, the 

 corresponding values of the contraction produced by a magnetic field of 

 200 c.g.s. units, we find that the points for both the direct and alternating 

 magnetic fields lie very approximately on two straight converging lines. 

 When the load of - 5 x 10 5 grammes per sq. cm. is on the wire these two lines 

 when produced meet at the point marked 870 x 10 6 on the scale of rigidity, 

 which means that, if it were possible to have a nickel wire of rigidity 

 870 x 10 6 grammes per sq. cm., the contraction due to the action of the direct 

 and the alternating magnetic fields of 200 units would be of the same 

 amount. When the longitudinal load on the wire is 2 x 10 5 grammes per 

 sq. cm. in the same way, the plotted results give two straight lines which 

 when produced meet at the point marked 850 x 10 6 on the scale of rigidity 

 These values are, of course, imaginary, as it is not likely that the material 

 nickel could be put into such a physical state that its rigidity would be 

 either of the values mentioned above. 



