Page:Proceedings of the Royal Society of London Vol 60.djvu/80

Rh greater than the magnetic moment when warm, when the permanent state had been reached. But it will be noticed from the diagrams (see 1 3 ) that in the case of the 7'65 per cent, nickel stee], 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 Magnetised Iron, $c., cooled to Temperature o f L iquid A ir. 65

F ig. 14.—Nickel steel. Ni = 19 *64 C =0*19 Si = 0 -27 Mn = 0 -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 magnetic 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