842 Magnetic Properties of Graded Series of Chrome Steels. 



beyond that point however, tend to lower the position of 

 the crossing point in the range. 



In the case o£ the annealed specimens, again, the effect 

 o£ lowering the temperature to —190° C. is not merely a 

 temporary effect which passes away when the temperature 

 is allowed to rise again, but immersion in liquid air produces 

 in the specimen a permanent effect, lowering its susceptibility 

 for low fields and raising it for high, and the crossing points 

 of the two curves taken at room-temperature, one before and 

 one after immersion in liquid air, vary in position exactly as 

 do those of the curves I and I', the crossing for the speci- 

 men containing 12 per cent, chromium occurring at a higher 

 point in the range than any of the others. 



Briefly, then, the results of this investigation may be 

 summarized as follows : — 



(1) The effect of lowering the temperature of a chrome 

 steel is to diminish its susceptibility for low fields and to 

 increase it for high fields. 



(2) The crossing of the curves at 15° C. and at -190° C. 

 in the annealed condition takes place for higher values of 

 the magnetizing force as the chrome content is increased up 

 to 12 per cent., but further additions after that point lower 

 the value of the field for which crossing occurs. 



(3) Immersion in liquid air produces a permanent effect 

 on the annealed specimen, which is not wiped out when the 

 temperature is allowed to rise to room-temperature again. 



(4) For specimens in the quenched condition the crossing 

 of the curves at 15° C. and — 190° C. occurs for very high 

 values of the magnetizing force, probably much greater than 

 160 c.G.s. units. 



(5) Immersion in liquid air has no permanent effect on 

 quenched specimens ; and 



(6) In both the annealed and quenched conditions the 

 residual magnetism and the coercive force are greater at 

 -190°C. than at 15° C. 



In conclusion, I desire to express my thanks to Pro- 

 fessor Gray and to Dr. J. G. Gray for the interest they 

 have taken in the progress of the work. 



