PROPERTIES OF IRON AT A HIGH TEMPERATURE. 
401 
Per cent. Per cent. 
0 
•74 
•73 
Si 
•50 
•55 
s 
•05 
•06 
p 
•08 
•09 
Mn 
11-15 
12-00 
It is well known that this steel at ordinary temperatures, and for both great and 
small magnetising forces, is but very slightly magnetic. The object of these experi¬ 
ments was to ascertain whether it became magnetic at any higher temperature. 
The dimensions of the ring were as shown in the accompanying section ;— 
Thus the mean area of section is 1'7 sq. cm., and the mean length of lines of 
magnetic force 12'3 cms. The ring was wound with 52 convolutions for the secondary 
and 76 convolutions for the primary. It was not possible to accurately estimate the 
mean area of the secondary; it is, however, assumed to exceed the mean area of the 
steel by as much as the secondary of the sample of wrought iron is estimated to 
exceed the area of that sample; this gives an area of 2'38 sq. cms. 
A preliminary experiment at the ordinary temperature gave induction 67’7 ; 
magnetising force 26'9. 
The induction in the airspace between the wire and steel will be 26'9 X 0'68 = 18’3; 
deducting this from 67'7, we obtain the induction in the steel equal to 49’4, or 29'0 
per sq. cm.; dividing this by 26’9, we obtain 1'08 as the permeability from this 
experiment. 
After the ring had been heated to a high temperature, about 800° C., and had been 
allowed to cool, a second experiment gave total induction 76, magnetising force 22’8, 
permeability 1'5. 
The ring was again heated and allowed to cool, observations being made both 
during rise and fall of temperature, with the following results :— 
