512 Proceedings of the Royal Society of Edinburgh. [Sess. 
500° C. to 700° C. there is a gradual falling off in magnetic quality ; and 
finally the susceptibility becomes zero at 770° C. 
It will be seen that the susceptibility-temperature curves for this high 
carbon steel present precisely the same general features as those which 
characterise the specimen of cast iron. 
Medium Carbon Steel . — On testing the specimen of medium carbon 
steel very similar results were obtained. An improvement in magnetic 
quality takes place as the temperature rises from room temperature to 
150° C. ; this is followed by a falling off, and then a further improvement, 
in magnetic quality. This improvement continues until the critical 
temperature is approached, when a very rapid falling off in magnetic 
susceptibility takes place. 
