10 
ME. .1. EEGINALD ASHlVOETH; 
8. With the object of comparing the magnetisation curves of drawn steel wire 
when cold and when hot, and also of determining the relation of the temperature 
coefficient to the intensity, another series of experiments was undertaken. A wire. 
No. H 30,* was selected of the same diameter and gauge as one upon which a number 
of experiments had previously been made;! it was 0‘187 centim. in diameter, and its 
length was 85’3 centims., so that the dimension ratio was 456 and the demagnetising 
factor negligibly small. The wire was fixed in a glass tube in an upright solenoid, 
33'2 centims. from the magnetometer, and the usual arrangements were adopted 
for tracing the curve of magnetisation according to the one-pole method of Ewixg. 
In all the experiments the vertical component of the earth’s force was neutralized. 
After some prelimina,ry heatings and coolings the Avire Avas carried through a series 
of graded magnetic cycles at air temperature ; then, after demagnetisation, a current 
of steam was passed and maintained through the tube, and the same series of graded 
cycles Avas repeated, the forces used at either temperature being exactly alike. It 
AA'ill he seen from Diagram IV. that the susceptibility of the hot Avire when the force 
Diagram IV. 
Piano Steel "Wire. 
* Wires marked with the letter H were kindly sujiplied by Mr. W. D. Houghtox, of V arrington. 
t ‘ Eoy. Soc. Proc.,’ a'oI. 62, p. 210. 
