196 Dr. Harrison on Variation with Temperature of 
The lower limit of the interval is rather indefinite. If, 
however, we compare the magnetic critical interval with the 
range of temperature in which thermoelectric changes occur *, 
it is seen that the Peltier coefficient for nickel undergoes 
a change between the temperatures 290° and 375°, the 
alteration in slope of the curve at the latter point being 
very abrupt. 
The change in slope in the resistance-temperature curve 
for the same specimen occurs between the temperatures 320° 
and 375°. 
For iron, the thermoelectric change occurs between 750° 
and 860°, while an alteration in its coefficient of resistance 
extends over the interval between 750° and 850°. 
Thus it is seen that for both nickel and iron there is a very 
good agreement between the magnetic critical interval and 
the range of temperature within which thermoelectric and 
resistance changes take place. The agreement is rather 
more complete in the case of nickel than it is in the case of 
iron, probably on account of the greater purity of the nickel 
specimen employed. The fact that the critical temperature 
for nickel is about 50° higher than that usually quoted for 
the meta] is also probably to be accounted for in the same 
way. 
Since the completion of this paper, Messrs. Honda and 
Shimizu also find the magnetic critical point for a specimen 
of nickel to be “just under 400°.” They also show that the 
‘contraction under magnetization ” vanishes asymptotically 
as the temperature approaches the critical point. 
Part of the heating apparatus and the solenoid used in 
these experiments were made at University College, London, 
where the general method was suggested by Professor 
Callendar, F R.S., to whom I desire to acknowledge my 
indebtedness. I also wish to express my thanks to Professor 
H. F. Weber, for many suggestions given and kindly interest 
shown during the course of this research, 
Physik Gebatde, 
Zirich. 
* Page 188, Phil. Mag. Jan. 1902. 
t+ Honda and Shimizu, Phil. Mag. Oct. 1908. 
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