Magnetised Iron, #<?., cooled to Temperature of Liquid Air. 63 



magnets arrived almost immediately at their permanent condition, in 

 which the magnetic moment, when cold, was greater than the mag- 

 netic moment when warm by about 12 per cent. The variation of 

 magnetic moment in the case of these magnets is shown by the dia- 

 grams 4, 5, 6, and 7, in which the firm lines represent the magnetic 

 moment when the magnet is at 5 C., and the dotted lines the mag- 

 netic moment at 185 C. It will be seen, therefore, that in the 

 case of the magnets there was 110 such initial decrease of magnetisa- 

 tion as in the case of the carbon steel magnets. The analysis of these 

 steels was furnished to us by Mr. Haclfield, and is appended to the 

 diagrams. These steels are all in their hard condition, and possess 

 considerable coercive force. 



Aluminium Steels. The aluminium steels employed had the follow- 

 ing percentages of aluminium, viz. : O72, 1/16, and V60. In all 

 these cases the first effect of cooling the magnet made of these steels 

 was to cause a very small diminution in the magnetic moment, but 

 not more than about 2 per cent, (see figs. 8, 9, and 10). The subse- 

 quent rise in temperature of the magnet again to its ordinary tem- 



foo- 



/oo- 



FIG. 8. Aluminium steel. 



Al = 

 C = 



Si = 

 Mn = 



0-72 

 0-20 

 0-12 

 0-11 



Fe = 98 '85 



FIG, 9. Aluminium steel. 



Al = 1-16 

 C =0-26 

 Si = 0-15 

 Mn - 0-11 

 Fe = 98 -32 



loo 



5c 





FIG. 10. Aluminium steel. 

 Al = 1-60 

 C = 0-21 

 Si = 0-18 

 Mn = 0-18 

 Fe = 97 '83 



perature, caused a still further fall in magnetic moment, and from 

 and after that point the effect of cooling down to the temperature of 



