1908-9.] Low Temperature Experiments in Magnetism. 
287 
XV. — Low Temperature Experiments in Magnetism. By James G. 
Gray, B.Sc., Lecturer on Physics in the University of Glasgow, 
and Hugh Higgins, M.A., Thomson Experimental Scholar in the 
University of Glasgow. Communicated by Professor A. Gray, 
F.R.S. 
(MS. received February 15, 1908. Read same date.) 
The alterations brought about in the magnetic moments of magnets, 
composed of various metals and alloys, by alternate cooling and warming 
between ordinary room temperature and that of liquid air have been very 
fully investigated by Dewar and Fleming.* It was found by these 
experimenters that in the case of most of the metals examined the effect of 
the first cooling upon the magnet — which had previously been magnetised 
to saturation in the field of an electromagnet — was to bring about a very 
considerable reduction in its magnetic moment. On allowing the magnet to 
warm to room temperature its magnetic moment still further diminished. 
On cooling once more to the liquid air temperature the magnetic moment 
increased, and from and after this stage it was found that the magnetic 
moment of the magnet when cold exceeded that of the magnet when at 
room temperature by a definite amount. The changes brought about by 
the treatment were found to be much greater in the annealed than in the 
quenched condition of the material. 
In a few cases, notably that of the chromium steels, the effect of the first 
cooling was to increase the magnetic moment ; in other cases the treatment 
caused very little alteration in the magnetic moments of the specimens. 
In the experiments of Dewar and Fleming the specimens were 
magnetised initially at room temperature. It occurred to one of the 
authors of the present paper to repeat the procedure, starting with a 
specimen magnetised to saturation when at the temperature of liquid air. 
On carrying out such an experiment it was found that the changes produced 
by the treatment differed in many respects from, and were even more 
remarkable than, those observed by the aforementioned investigators. 
The method of experimenting was as follows : — A short bar of the metal 
to be examined was placed within a glass tube bent up at one end to admit 
liquid air. The end of the tube through which the specimen entered was 
closed by means of a cork, and the tube thoroughly wrapped up in cotton- 
* Proc . Roy. Soc., vol. 60, p. 57. 
