412 Proceedings of the Royal Society of Edinburgh. [Sess. 
heatings, and so on. It will be seen that the percentage diminution in 
susceptibility brought about by the first heating was greatly in excess of 
that caused by any subsequent heating. Each heating, however, resulted 
in a diminution of magnetic property, and so far as the experiments went 
there is no appearance of a steady state having been set up. 
The magnetic properties of the Heusler alloys when quenched from a 
high temperature are very remarkable. Diagram V. shows the results ob- 
tained on testing a specimen in both the normal and the quenched conditions. 
Curve I. was obtained with the specimen in the normal, or unquenched, 
condition ; Curve II. was obtained with the specimen in the quenched condi- 
tion ; Curve II/ with the specimen completely immersed in liquid air. Curve 
III. shows the magnetic behaviour of the specimen after two quenchings, 
and Curve III/ its behaviour in the doubly quenched condition when at the 
temperature of liquid air. It will be seen that the effect of the low 
temperature is to greatly increase the susceptibility of the material. The 
Heusler alloy in this respect resembles Hopkinson’s nickel-iron alloy con- 
taining 25 per cent, of nickel. It is interesting to note also, in connection 
with the comparison of the two materials, that in the Heusler alloy we 
have a material composed of non-magnetic metals which is strongly 
magnetic, whereas in the case of the nickel-iron alloy we have an example 
of a material composed entirely of magnetic metals which is initially non- 
magnetic at ordinary temperatures. 
As on former occasions, the author desires to express his indebtedness 
to Professor Gray, in whose laboratory the work described above has been 
carried out. 
(. Issued separately July 23, 1908.) 
