268 Professor Fleming on Electric Research. [June 5, 



the magnetic moment of the magnet, whilst the separation of the 

 molecular groups and the reverse effects ensue on heating. The 

 action of the low temperature upon soft iron and upon magnetised 

 steel would be explicable then if we may legitimately make the 

 assumption that lowering the temperature approximates the molecular 

 groups and also the members of each group. 



The result of this, in the case of existing permanent magneti- 

 sation, is to close up more or less those groups which are in an 

 unstable condition, but to increase the co-lineation in those groups 

 in which the magnetic moment exceeds a certain value. Hence, in 

 the case of the permanent magnet, the first effect of sudden cooling is 

 a compound effect ; it consists in a great reduction of the magnetic 

 moment of certain unstable groups, but in an increase of moment of 

 others. After this initial stage is past, the normal effect is an 

 increase of magnetic moment of the groups by bringing the members 

 of them closer together, and a diminution by increase of distance. 

 There remains then to be explained the anomalous behaviour of the 

 nickel-steel and hardened iron, but an attempt to throw an inner 

 light upon the results obtained with these substances cannot possibly 

 be successful until we have explored far more thoroughly, at low 

 temperatures, the changes in mechanical as well as magnetic 

 qualities. 



Much as we may be tempted to speculate upon the causes of 

 these various changes in the properties of matter at very low tem- 

 peratures, a more important duty at the present time is the collection 

 of facts and the completion of accurate quantitative measurements. 

 The experimental difficulties of this low temperature research are 

 very great, but both Professor Dewar and I have been chiefly anxious 

 in this particular work to prosecute preliminary explorations in 

 as many regions of it as possible, these pioneering experiments 

 enabling us to ascertain in what direction further inquiry will be 

 profitable. Every step forward opens up fresh suggestions for 

 investigation, and, I may add, fresh difficulties. In the light of the 

 results, however, thus ascertained, we shall have additional means 

 of testing and judging existing electrical theories, and the facts 

 themselves, when built into the fabric of scientific knowledge, will 

 serve to broaden those foundations on which we may profitably erect 

 new hypotheses of electric and magnetic phenomena, which, even if 

 they can do but little to dissipate that mystery which enshrouds the 

 most familiar facts, will serve as a continual stimulus to thought and 

 work in days and years that are yet to come. 



f J. A. F.] 



