622 Proceedings of the Royal Society of Edinburgh. [Sess. 
The values of the “ sensitive states ” are expressed in the usual manner, 
as the percentage by which the magnetic intensity for the specimen in the 
“ sensitive ” condition exceeds the normal value. The figures for the steel 
wire and the hard steel are taken for fields of 12 and 10 c.G.S. units 
respectively, those being the magnetic forces for which the effect is about a 
maximum. The results are the means of three tests, which are in excellent 
agreement. They show that the “ sensitive state ” produced by a certain 
rise or fall of temperature may greatly exceed that produced by a cycle 
consisting of the rise and the fall imposed in succession without intermediate 
testing and wiping out. 
Specimens kept steady for an hour at —190° C. showed no alteration. 
“ Sensitive State ” at high temperatures . — The authors now proceeded 
to carry out a similar series of experiments at high temperatures. For this 
Fig. 3. 
purpose a special arrangement for heating the specimens was adopted. In 
the preliminary experiments the bars had been annealed in a Fletcher gas 
furnace, and were thereafter removed to the solenoid of the magnetometer. 
Although they were handled with the greatest care, occasional slight 
jarring was inevitable. It was therefore decided to subject the specimens 
to the heating process while in their position in the magnetising coil. For 
this purpose an electric furnace was fitted as shown in section in fig. 3. 
A A represents the magnetising solenoid which was wound in four layers, 
of which only one is shown in the sketch. B B is a water jacket, with an inlet 
tube at C and at outlet at D. E E is a porcelain tube, on which a length of 
fine platinum wire is wound non-inductively, and the terminals are mounted 
on a slate frame at F. This furnace is placed within a tube of Jena glass 
GG, the intervening space being packed with kaolin clay HH, which 
prevents the coils of the platinum wire from altering their position on the 
porcelain tube when expanded by the heating. A thick sheet of copper 
