296 Dr. Richardson and Mr. Laws on Changes in the Magnetic 



For instance, the Aphometer might be put bodily into the 

 bell-jar of an air-pump, the wires passing into it. By this 

 means the experimenter would have a better chance of success, 

 as some distressing complications would be eliminated when 

 a dry neutral atmosphere surrounded the contacts. 



I am glad to thank Professor W. H. Heaton, M.A., for 

 his kindness in always placing the resources of this laboratory 

 freely at my disposal. 



XXIV. On some Interesting Changes in the Magnetic Condition 

 of an Alloy of nearly Pure Iron and Aluminium (2*42 °/ ) 

 due to successive Heatings and Coolings. By S. W. 

 Richardson, D.Sc, Principal and Professor of Physics at 

 the Hartley College, Southampton, and S. C. Laws, B.Sc, 

 Research Student at the University College, Nottingham*. 



THE behaviour of alloys is attracting so much attention 

 at the present time that the authors felt that the curious 

 phenomena which they have observed might be of interest to 

 some observers who are studying this subject, although the 

 investigation of the magnetic properties of the specimens dis- 

 cussed in this paper is far from complete. An account of 

 some experiments on the same subject by one of us is given 

 in the Philosophical Magazine for January 1900. 



In this paper it is shown that the effect of temperature on 

 the magnetic behaviour of impure alloys of iron and aluminium 

 is very different from that on the behaviour of iron itself. 



It is shown that the curves connecting the permeability 

 and temperature for a constant field have at least two maxima, 

 which is explained by assuming that the specimens investi- 

 gated consisted of two distinct constituents. 



Subsequent microscopic examinations have shown the 

 presence of crystals in all the specimens except one. 



This demonstrates to us clearly that there are at least two 

 constituents present in the specimens. 



The subject was of so interesting a nature that it was 

 decided to continue the investigation, dealing in the first 

 instance with very pure specimens. 



A series of these were accordingly obtained from Professor 

 Arnold, of Sheffield. The behaviour of the first one, which 

 is the only one we have investigated so far, was so striking 

 that we thought it worth while to publish at this early stage 

 a short account of some of our experiments. The specimen' 

 referred to contained about 2*42 per cent, of aluminium. 



* Communicated by the Authors. 



