Magnetization and Magnetic Change of Length. 661 



irreversible nickel-steels, the magnetization at ordinary 

 temperature can have any value whatever within given limits, 

 if the cooled specimens be heated to a suitable temperature. 

 Becquerel, who first studied the magnetic properties of 

 irreversible nickel -steels, found that in the alloy there 

 were two states of stable equilibrium; but according to 

 our results there are an infinite number of such states, a fact 

 which may possibly prove to be important in the theory of 

 molecular magnetism. 



Comparing the magnetization at different temperatures in 

 these nickel-steels, we notice that the critical temperature in 

 the descending branch of the temperature-cycle generally 

 becomes less as the percentage of nickel decreases. As 

 the content of nickel diminishes from 70*32 per cent, to 

 26'64 per cent., the critical temperature falls from several 

 hundred degrees to the ordinary temperature. It is then 

 highly probable that 25 per cent, nickel-steel, which is feebly 

 magnetic both at ordinary and liquid air-temperatures, would 

 become strongly magnetic, if the cooling should be pushed 

 still further. If it once become strongly magnetic by cooling, 

 it may preserve this property, after the alloy is heated to 

 the ordinary temperature. It will be interesting to investigate, 

 whether other non-magnetic alloys, which consist of a mag- 

 netic and a non-magnetic metal, would display a similar 

 phenomenon on being cooled to a sufficiently low temperature. 

 The fact that the two strongly magnetic metals form a non- 

 magnetic metal is then nothing more than the lowering of 

 the critical temperature of the alloy to the ordinary tempera- 

 ture. Owing to some changes occurring in the molecular 

 configuration during the process of fusion of the constituent 

 metals, the critical temperature of the alloy in the descending 

 branch of the temperature-cycle falls to a low temperature, 

 and therefore the alloy behaves as a weakly maguetic or 

 non-magnetic alloy at ordinary temperature. The same 

 remark will also apply to a non-magnetic alloy which consists 

 of a magnetic metal and a non-magnetic one. The above 

 view is also favoured by the fact that in irreversible alloys 

 the hysteresis-loss at ordinary temperature is markedly small, 

 which corresponds to the hysteresis of iron or nickel at high 

 temperatures, but its value at a low temperature considerably 

 increases, corresponding to the hysteresis of the same metal 

 at ordinary temperature. 



