112 



Scientific Proceedings, Royal Dublin Society. 



pi'evious experiments, with a coustaut load ou of 10° grammes per sq. cm., 

 the -gVth part of the tenacity of iron, and, before testing, they were, as in 

 the first series, all passed twice through a bunsen flame and carefully 

 annealed. 



To find, however, the effect of annealing on the material, one of the 

 wires — a No. 16 — was tested in the condition in which it came from the 

 manufacturer ; it was then annealed and again tested, with the result 

 shown in fig. 6, where the area of the cyclic curve is increased about six 

 times by the annealing. 



Angle of Twist. 

 Fig. 6. 



These iron wires were very much softer and better magnetically than 

 those used in the first set of experiments, as may be seen by comparing 

 the areas of the cyclic curves in the two cases when the same size of 

 wire — No. 16 — was used, and the same load on, and when in the same 

 magnetic field of 0-45 c.g.s. units. When plotted to the same scale, the 

 area given by the new wire is about two and a half times that given by 

 the othei'. 



The curves in fig. 6, and all the curves drawn to obtain the values 

 for the curve in fig. 7, were plotted to a different scale from the previous 



