PROPERTIES OE IRON AT A HIOH TEMPERATURE. 
447 
incluction in the iron 109, or 57 per sq. cm., giving permeability equal to 1‘14, 
showing that the material lias suddenly become non-magnetic. 
The ring was now allowed to cool, some rough experiments being made during 
coolino-. When cold the resistance of the secondary and the leads was found to be 
0‘697 ohm. The ring was again heated till the resistance of the secondary readied 
2‘845 and the magnetism had disappeared. It was next allowed to cool exceedingly 
slowly, and the following observations were made with a magnetising force of 
0'075 C.G.S. unit:— 
Resistance of secondaiy 
Temperature . . . . 
Incluction per sq. cm. 
2-81 
796° 
0 
2-80 
792° 
0 
2-79 2-78 2-76.5 
788° 785° 781° 
V- ^ -y 
0 126-8 
showing that magnetisation returns at a temperature corre.sponding to resistance 
between 2‘78 and 2‘765. 
Systematic observations then began. Tlie results are given in the following tables 
and the curves to which reference is made. The curves are in each case set out to 
two scales of abscissae, the better to bring out their peculiarities. 
Tables 1-4. 
Table 1, Curve II. 
Table 2, Curve III. 
Resistance of second-' 
ary before experi- 
^ 2-76 
2- 
75 
ment 
TemjDerature of 
se-' 
condary before 
ex- 
^778°C. 
775 
° C. 
peri ment 
- 
Resistance of second-' 
ary after experi- 
^ 2-75 
2- 
73 
ment 
Temperature of 
se-' 
condary after 
ex- 
^775"C. 
767 
0 . 
periment 
J 
Magnetising 
Induction per 
Maanetisino- 
Induction 
force. 
sq. 
cm. 
force. 
per sq. cm. 
0-075 
511-8 
0-075 
494 
i 0-15 
1313-9 
0-15 
1033 
0-3 
2482-6 
0-30 
3286 
0-6 
32 
57-4 
0-6 
4520 
1-2 
3659-2 
1-2 
5.367 
2-4 
4104-0 
2-4 
5668 
4-4 
4520-0 
4-2 
6056 
7-8 
6228 
12-8 
6587 
45-2 
6945 
Table 3, Curve IV. 
2-72 
76.3° C. 
2-695 
754° C. 
Magnetising- 
force. 
0-075 
0-15 
0-.3 
0-6 
1-2 
2-2 
7-6 
13-0 
46-6 
Induction 
per sq. cm. 
328 
260 
710 
635 
' 2:304 
5281 
6544 
7318 
8036 
8323 
8581 
Table 4, Curve V, 
2-67 
2-66 
741° C. 
Magnetising 
force. 
0-075 
0-15 
0-3 
0-6 
2-2 
7-6 
47-2 
Induction 
per sq. cm. 
227 
180 
473 
425 
1281 
1172 
5377 
8165 
9-295 
9781 
