168 



BRUSH— SPONTANEOUS GENERATION OF HEAT [April 22, 



work of some sort sufficient to lift the steel bodily about 800 feet 

 high against the force of gravity. 



I next prepared a batch of " high-speed " tungsten steel consist- 

 ing of the same number of bars of the same dimensions as in the 

 first experiment. The bars were water-hardened at white heat, 

 not far below the fusing point, brought to room temperature, oiled 

 and introduced just as in the former case, and galvanometer read- 

 ings were commenced an hour after hardening. 



10 20 30 40 50 00 70 80 



Hours After Hardening 

 Fig. 3. 



Fig. 3 shows the curve of heat generation in the " high-speed " 

 steel, and the curve of normal cooling located with respect thereto 

 as in Fig. 2. The cooling curve here shown is the lower part of 

 that used in Fig. 2. It is permissible to use the same cooling curve 

 for both kinds of steel because the thermal capacity of the two lots 

 was very nearly the same. 



It is seen that heat generation in the tungsten steel was the same 

 in character as in the carbon steel of Fig. 2, though much less in 

 amount and somewhat more persistent. 



Many workers in steel are aware that the metal expands a little 

 when hardened, and shrinks when annealed ; but I have not met 

 with any quantitative data on the subject. With the hope of throw- 

 ing some light on the spontaneous generation of heat already de- 

 scribed, I investigated this phenomenon of swelling and shrinking 

 as follows : 



