BRUSH— GENERATION OF HEAT IN STEEL. 355 



ratus no test of hardness was at that time made. The twelve bars 

 (specimen B) were next annealed by slowly heating to full decales- 

 cence and then allowing to cool very slowly in the furnace. As 

 expected, no trace of heat generation followed this treatment which 

 was made for checking purposes. 



Before commencing the experiments with specimens A and B, a 

 test bar of each lot was prepared for accurate length measurements 

 which followed each treatment. The very interesting results of 

 these measurements, differing materially in the two specimens, were 

 tabulated and compared. 



The present (third) paper deals with some later experiments 

 prompted by the anomalous behavior of specimen B of the Hadfield 

 nickel-chromium steel after its third quenching described above. 



In conducting these experiments an electric furnace was em- 

 ployed for heating, instead of the less convenient gas furnace for- 

 merly used, and the latest form of " sclerescope " for testing hard- 

 ness was installed ; also, a most modern industrial thermo-electric 

 pyrometer. The latter was used as it came from the maker, without 

 further calibration ; hence the temperatures recorded in this paper 

 may be several degrees in error, though they are thought to be rela- 

 tively consistent. 



The apparatus employed in detecting, measuring and following 

 the progress of heat generation in the steels under treatment was 

 fully described and illustrated in each of the former papers, and it is 

 thought best to omit another description here. 



It will be recalled that '' specimen B " was left in the annealed 

 condition. In this condition it was subsequently found to have a 

 scleroscope hardness of 31. This is the mean of many consistent 

 measurements. Each scleroscope hardness cited in this paper is the 

 mean of at least ten consistent measurements, each measurement 

 made on a fresh spot of surface carefully made smooth and fiat. 



In order to ascertain the critical temperatures of decalescence 

 and recalescence of " specimen B," three of the twelve bars were 

 very gradually heated until almost complete loss of magnetic 

 susceptibility was reached. This occurred rather abruptly at about 



