1908-9.] Magnetic Properties of certain Copper Alloys. 
275 
copper has been varied. This scheme was adopted because the effect of 
variation of the ratio of manganese to aluminium had already been 
investigated by Heusler, Starck, and Haupt,* and also because certain 
considerations seemed to indicate that copper played a not unimportant 
part in the magnetism of the Heusler alloy. f 
The specimens from castings B, D, and E were of uniform size, viz., 
cylinders of length 20 cm. and diameter about 1 cm. They were tested in 
the condition as cast, except that the ends were cut off square. No further 
dressing was given as that process would probably have altered the 
magnetic properties slightly owing to the heat evolved in the operation. 
The materials included under (4)-(10) in the above list were too 
feebly magnetic to lend themselves to testing in the usual magnetometric 
method. The specimens were accordingly cast in the form of small cylinders 
8 cm. in length and 6 mm. in diameter, and were magnetised by means of 
a powerful electromagnet. 
Apparatus . — For testing the castings B, I), and E the Gray- Boss 
magnetometer j was used. Alloys D and E exhibited only feeble magnetic 
properties, and the obtaining of a hysteresis cycle with the material in the 
quenched condition was a matter of very considerable difficulty. Such 
tests had to be carried out in the early morning hours, when the slight 
disturbance of the magnetometer zero due to electric earth-currents was at a 
minimum. 
The magnetisation of the specimens included under (4)-(I0) in the above 
list was carried out with the large electromagnet belonging to the Physical 
Laboratory of Glasgow University. The magnet is of cast steel with a 
permeability almost coincident with that of wrought-iron. It is rectangular 
in shape, measuring about 100 cm. in length and 40 cm. in height. In 
addition to the coils on the poles, the whole length of the yoke is wound. 
During the experiments the pole-pieces were kept 11 cm. apart in order to 
freely admit the specimens when enclosed in vessels for holding liquid air. 
With this separation a field of 4400 C.G.S. units was obtained on exciting the 
magnet with the current from a 110- volt storage battery. The permanent 
magnetism so induced in the specimens was measured by a delicate magnet- 
ometer, the motion of whose needle and mirror was observed by means of a 
scale placed more than two metres distant. 
Quenching and Liquid Air Tests . — In the previous paper an account has 
* “ Magnetisch-cliemische Stnclien,” Per. cl. Deutsch. Pliys. Gesell., 1903, S. 220. 
t See article by J. G. Gray and A. D. Ross, Pliys. Zeit ., x., No. 2, S. 59. 
J. G. Gray and A. D. Ross, “ On an Improved Form of Magnetometer, etc.,” Pror. Roy. 
Soc. Edin., 1908-9. 
