406 Proceedings of the Royal Society of Edinburgh. [Sess. 
out and connected to a pair of terminals t, t as shown in the figure. On 
passing an electric current of suitable strength through the platinum wire 
it was possible to bring the interior of the porcelain tube, and consequently 
the specimen, to any desired temperature. 
The external diameter of the glass tube being very slightly less than 
the internal diameter of the magnetising solenoid, the furnace could be 
slipped as a cartridge within the solenoid. 
Between the furnace and the magnetising coil was a water-jacket J, 
through which a stream of cold water was kept circulating. 
The various temperatures employed in the course of the investigation 
were measured by means of a platinum, platinum-iridium pyrometer. In the 
experiments contained under (1) and (2) above, the magnetising solenoid, 
with the furnace in position, was adjusted so that its axis was on the east- 
and-west line passing through the magnetometer needle. The specimen, with 
the pyrometer, was then placed in position and the test proceeded with. 
Experiments at Low Temperatures. 
In carrying out the experiments at low temperatures the furnace was 
removed, the specimen placed in a glass tube well served with cotton- 
wool, and the whole slipped within the solenoid. One end of the glass tube 
was closed ; the other end was open, and the tube was bent up to allow of 
liquid air being poured in. 
Preliminary Experiments. 
Preliminary experiments were made with a view to testing the adjust- 
ment of the apparatus and of ascertaining whether the various specimens 
varied among themselves. On placing the rods in turn within the coil and 
carrying out a test, I-H curves were obtained which were practically 
identical. One of the curves so obtained is shown in Diagram IV., Curve I. 
Experiments contained under (1) above. 
The experiments (1) were now proceeded with. The specimen was 
carried through a cycle in the usual way, the temperature being that 
of the room (15° C.). A current was now passed through the heating coil 
of the furnace, which resulted in a steady temperature of 120° C. being set 
up. With the specimen at this temperature a cycle was gone through. 
This procedure was repeated for various temperatures, and the results 
