on the Magnetic Properties of Iron. 

 Fig. 4. 



18000 

 16000 

 14000 



12000 

 10000 

 8000 

 6000 

 4000 

 2000 



100° 200° 300° 400° 500° 600° 700° 800° 

 Temperature in Degrees Centigrade. 



The following values were obtained with a force of about 

 0-0285 c.g.s.:— 



Temp.jn j 150 2 q Q0 4g20 592<5 M5 o 7350 74 go 767 o 

















1 









H-- 



■ 0/7 



? C.& 



s 



























































/ 























































H, 





















* 







deg. C. 



327 491 819 1310 2620 3275 6175 



With still weaker fields the kicks in the galvanometer on 

 reversing the magnetizing currents were very small, and the cal- 

 culated permeability could not be relied upon with any degree 

 of accuracy ; but from the observations taken with a magnetic 

 force as low as 0*009 C.G.S. the permeability was found to 

 increase rapidly as a temperature of 770° C. was approached, 

 from which it would appear that even with this very weak 

 field the second stage is brought on before the critical 

 temperature is reached. 



If the effect of heat in hastening the transition from stage 

 to stage is uniform — that is, proportional to the temperature — 

 there will be no sudden increase in the permeability as the 

 temperature is raised until the second stage is entered upon; 

 but if the rate of transition increases with the temperature, a 

 considerable augmentation of susceptibility can be thus 

 accounted for without assuming that the second stage is 

 brought on. 



Figs. 2, 3, and 4 are given to show the relation between 

 permeability and temperature under magnetic forces which 

 bring on the respective stages of the magnetizing process 

 before any heat is applied. Jt will be seen (fig. 2) that with 

 a fairly strong field the permeability is only slightly affected 



