in C.G.S. Units. 
510 Proceedings of the Royal Society of Edinburgh. [Sess. 
that for a value of the magnetising force of 5 c.g.s. units the magnetic 
quality at first steadily increases with the temperature to a maximum at 
about 230° C. ; from 230° C. to 270° C. it diminishes, and from this point it 
continually increases, reaching a second maximum at about 730° C. ; further 
increase of the temperature brings about a rapid diminution in susce pti- 
Fig. 1. — Specimen of cast iron. 
bility, and the material becomes non-magnetic at about 770° C. The 
corresponding curves for higher values of the magnetising force present 
the same general features. For H = 30 c.g.s. units the curve slopes upward 
until the temperature becomes 220° C., after which there is an abrupt 
falling off in magnetic quality, succeeded by an abrupt increase, and a 
second maximum is arrived at when the temperature reaches 300° C. From 
300° C. to 500° C. the susceptibility remains practically constant ; from 
