Magnetised Iron, $c., cooled to Temperature of Liquid Air. 65 



greater than the magnetic moment when warm, when the permanent 

 state had been reached. But it will he noticed from the diagrams (see 

 fig. 13) that in the case of the 7'65 per cent, nickel steel, the effect of 

 the first cooling was to cause a slight increase in magnetic moment. A 

 remarkable peculiarity, however, was found in the case of the 19'64 per 

 cent, nickel steel. In this case the effect of the first cooling was to 

 cause a very considerable reduction of magnetic moment, very nearly 

 50 per cent., that is to say, the magnetic moment fell instantly, on 

 cooling in the liquid air, to about half the value that it had at the 

 beginning of the experiment. On taking the magnet out of the liquid 

 air and allowing it to warm up again to the temperature of the room, 

 the magnetic moment immediately increased again, and from and after 

 that time the effect of the temperature change on the magnetic 

 moment was such that the magnetic moment, when cooled to the 

 temperature of liquid air, was always less than the magnetic moment 

 at 5 C. by about 25 per cent, of the latter value. These relative 

 changes are shown in the diagram (fig. 14). These experiments 



Joo 



loo- 



loo 



FIG. 14. Nickel steel. 



Ni = 19 -64 

 C =0-19 

 Si = 0-27 

 Mn = -93 

 Fe = 78 '97 



100-00 



with the 19 per cent, nickel steel were repeated a great many times, 

 and always with the same general results. The sample of 29 per 

 cent, nickel steel was then examined, and it was found that the mag- 

 netic changes produced in it on heating and cooling were of the same 

 general character as in the case of the 19 per cent, sample, only less 



