428 Mr. F. H. Pitcher on Effects of Temperature and 



The Curves of fig. 1. — The magnetic observations were 

 taken at thirteen different fields, curves for seven of which 

 have been plotted in fig. 1. The longitudinal field of the 

 solenoid is indicated for each pair of curves. Each pair is 

 drawn for the same field. Abscissae represent current in 

 the wire and ordinates longitudinal intensity of magnetization. 

 The curves drawn in full lines are for the observations taken 

 in a vacuum and at a higher temperature than those in dotted 

 lines, which are for the observations taken in air. Where the 

 curves coincide, showing no effect of temperature, full lines 

 are drawn. 



The curves shown in fig. 2 are the corresponding tempe- 

 rature-curves plotted to current in the wire. The lower of 

 these curves is that for the specimen in air. The points 

 marked with a cross belong to the observations in fields above 

 30 c.G.s. The middle curve is the temperature-curve in 

 vacuum for the higher fields ; while the top curve is that for 

 lower fields in vacuum, from 30 down. The temperature- 

 difference between the dotted and full-line curves for any 

 current in the wire can at once be found by consulting the 

 corresponding temperature-curves in fig. 2 on the same 

 ordinate. 



Considering the tables and the curves of figs. 1 and 2, it 

 will be noticed that the known behaviour of soft iron at constant 

 fields, as temperature advances, is well displayed. 



In high fields the dotted and full-line curves of each pair 

 separate almost from the start, and do not meet in any part 

 of their course, showing a continual decrease in intensity of 

 magnetization from the beginning as temperature increases. 



At a field of 10 c.G.s. there appears to be no change in 

 the intensity of magnetization for a temperature-difference of 

 350° C, as shown by the fourth curve (fig. 1) from the top, 

 together with the top and bottom curves (fig. 2) . 



At still lower fields the intensity begins to increase for a 

 comparatively small temperature-difference, as shown by the 

 two lower pairs of curves, fig. 1. The effect of the circular 

 field on the longitudinal component is here very marked. If 

 the dotted curves, where the temperature is less in evidence, 

 be considered, it will be seen that, in high longitudinal fields, 

 as the circular field increases there is but little change in the 

 longitudinal intensity. Somewhere between a longitudinal 

 field of 30 and 10 a point of inflection occurs, and the curves 

 below are changed in form entirely. At fairly low fields 

 (from 3*5 downwards) the drop with small increments of 

 circular field is at first very great, but soon reaches a limit ; 

 and the curves become very flat. 



The explanation of these effects is that for high longitudinal 



