204 DK. S. W. J. SMITH AND MR. J. GUILD: A THERMOMAGNETIC STUDY, ETC. 



practically the same, viz., 731 C. This is, therefore, according to these measurements, 

 the equilibrium temperature. 



The greatest accuracy cannot be claimed for our measurements of temperature, 

 although they were made as carefully as the conditions of experiment seemed to 

 warrant. Sometimes the thermocouple may have been used rather too often for 

 safety, between renewals and re-calibrations, but it is unlikely that the experimental 

 error in the measurement of temperature ever exceeded 5 C. 



Our general conclusion is that the equilibrium temperature can be measured, and 

 that it is, so far as our measurements can decide, substantially the same whatever 

 the percentage of carbon contained by the steel. 



21. Possible. Effects of the Presence of a Magnetic Field during Crystallisation. 



It is not inconceivable that the temperature at which the eutectoid separates out, 

 or disappears, should be influenced by the field. There is no evidence of this in the 

 curves which we have given, nor in others in which we have varied the field from 

 H = 10 to H = 400 C.G.S. 



To apply a severer test, we took " recalescence " (time-temperature) curves, using 

 a chronograph and a very open scale thermometer, with a specimen of the steel 

 containing 0'7 per cent, of carbon, placed between the poles of a large Du Bois 

 electromagnet. We could not detect any material difference between the temperature 

 of recalescence when the magnet was fully excited, giving a very intense field, and 

 that when the field was practically zero. 



Further, we attempted to determine whether the presence of an intense field made 

 any appreciable difference in the method of crystallisation of the eutectoid. Using 

 the rod containing 0'85 per cent, of carbon, we cooled it from above the eutectoid 

 point, between the poles of the electromagnet, first with its axis parallel to the field 

 and afterwards with its axis perpendicular to the field. In each case we examined 

 the subsequent magnetic behaviour of the rod at temperatures below 250 C. ; but 

 could not detect any difference between the changes accompanying the appearance 

 and disappearance of magnetism in the carbide in the two cases.* It is, therefore, 

 unlikely that the field produces any appreciable effect, during crystallisation at the 

 eutectoid point, upon the orientation of the carbide with respect to the iron. 



* Of. loc. at. 1 and 2. 



