18 Mr. R. L. Wills on the Effects of Temperature 



The following results were obtained with a magnetic force 

 of about 0-4 C.G.S. : — 



Temp in | 150 2660 37QO 46 g 513 o 591 o 63 . 2 o 64Q o 6i9 o 655 o 66 qo 

 deg. C. J 



fi Ill 137 188 256 470 491 735 769 994 1026 684 



It was found, however, just as in the case of iron, that the 

 permeability increases considerably as the temperature be- 

 comes rather high, even under extremely small magnetic 

 forces. 



Observations were taken at different temperatures as the 

 ring was cooled ; the magnetic quality returned as rapidly 

 as it disappeared when the temperature had fallen about 

 20° C. below the critical temperature, and for each mag- 

 netizing force the curves showing the relation between 

 permeability and temperature corresponding to heating and 

 cooling were found to be very similar to one another. 



Fig. 10 (p. 20) gives the permeability-magnetic force curves 

 for different temperatures plotted from the data given in 

 Table II., the scale of ordinates being the same for each curve ; 

 but the scale of abscissas in each case is regulated so that 

 the point of maximum permeability occurs at the same distance 

 along the horizontal axis. 



Table II. 





Magnetic 



Permea- 





Magnetic 



Permea- 





Force 



bility 





Force 



bility 





(H). 



(/*)• 





(H). 



00- 



188 





0-816 



111 





0-41 





245 



119 





1-63 



213 





4-08 



130 





2-45 



233 





5-71 

 7 34 



140 

 160 



Temperature 



3-26 



4-08 



243 



292 





8-97 



231 



before experiment 



4-89 



361 



Temperature 



11-42 

 13-76 



498 

 635 



370° C. 



5-71 

 6-52 



526 



697 



15° C. 



14-88 

 16-72 



647 

 646 



Temperature 



7-34 

 8-16 



787 

 847 





18-76 



611 



after experiment 



9-79 



847 





24-47 



512 



370° C. 



11-42 



785 





40-78 



322 



12-23 



756 





5701 



234 





1631 

 20-39 

 24-47 



621 

 511 

 434 



