HAYES. 



ERRORS m COOLING CURVES. 



15 



The faxjt that the heat liberated by the freezing lead causes no irregu- 

 larity in the cooling curves taken by the ordinary method, leads one to 

 believe that not only does that method fail to give the temperature of 

 transformation with accuracy, but it may fail to give any indication of 

 the existence of a transformation. On the other hand the possibilities 

 of the tube-form of couple are great. These possibilities are not fully 

 shown by Curve 11, as the junction was fairly heavy and the lime 



Fig. 3. 



coating much thicker than necessary. With a refined couple this lag 

 can be greatly reduced. 



The cooling employed in taking Curve 11 was about the same that 

 is employed in the oil-tempering of steel. At this rate of cooling a 

 refined couple would give very little lag, and should give curves suf- 

 ficiently accurate to throw considerable light on the processes of chil- 

 ling and tempering. 



Against the correcting /or temperature lig hy means of heating curve. 

 — A study of alloys in the light of Gibb's " Phase Rule " leads one 

 to believe that their characteristics depend greiitly on their past his- 

 tory. Having prepared an alh^y, it is doubtful if its ])roperties will be 

 the same after it has been remelted. It is then highly desirable that 



