244 Proceedings of the Royal Society of Edinburgh. [Sess. 
however, lessened to a certain extent the susceptibility for higher fields. 
The dotted curve shows the magnetisation curve which would have been 
obtained had the specimen been freshly annealed and tested up to 
H = 5 c.G.s. units. 
As is, of course, obvious, cyclic variation between wide limits of field 
strength destroys all trace of the “ sensitive state ” for fields lying between 
narrower limits. 
Scope of the Investigation . — So far, the tests were confined to a par- 
ticular variety of steel, annealed at 900° C. It was now decided to 
investigate this so-called “ sensitive state ” in various kinds of steel after 
subjection to varying thermal treatment. 
Rate of Cooling . — The experiments showed that in all varieties of steel 
the “ sensitive state ” was much less apparent in specimens quenched from 
high temperatures than in specimens slowly cooled. Further, it was shown 
that the magnitude of the effect did not depend to any large extent on the 
rate of cooling of the specimen, provided that the cooling was not very 
rapid. 
Effect of Temperature . — Very moderate temperatures are sufficient to 
