114 SCIENCE PROGRESS 



the crystalline mass being destroyed ; the transformation in- 

 volves very slight energy changes, as careful observation has 

 failed to afford any definite evidence of recalescence within the 

 transformation range. 



The alloys in which aluminium is displaced by some other 

 trivalent metal have been less studied but appear to behave in 

 a way quite like the above. Besides these, an alloy of a small 

 amount of iron with larger amounts of nickel and chromium is 

 strongly magnetic, whilst curiously enough an alloy containing 

 25 per cent, nickel and 75 per cent, iron is non-magnetic unless 

 cooled to a temperature somewhat below 0°, when it becomes 

 magnetic, and remains so until strongly heated ; consequentl}'-, 

 a bar of nickel steel may be cut in two parts and, after proper 

 treatment, under apparently the same conditions, the one piece 

 may be in the magnetic, and the other in the non-magnetic 

 condition. 



Within the last few years, alloys of iron with about 4 per 

 cent, of silicon have been found to be of great value for 

 commercial use in building transformers, as the hysteresis loss 

 may be considerably less when the transformer core is made of 

 such alloyed steel than when soft iron is used. 



From what has been said, it is evident that the study of the 

 magnetic properties of alloys is of great importance, both 

 because it seems likely to help us toward a better understanding 

 of the nature of magnetism and because of the technical improve- 

 ments which may result. It should, perhaps, be stated that 

 none of the alloys, except those containing large amounts of 

 iron, are valuable in commercial work. 



In conclusion, it is interesting to notice that Mr. O. C. Clifford 

 has found alloys of copper and tin more strongly diamagnetic 

 than copper itself, thus duplicating the phenomena of the 

 Heusler alloys among diamagnetic materials. 



