14 Reynolds and Moorby, Equivalent of Heat 



The rise was generally such as admitted of the tem- 

 perature of the brake being the same as that of the labo- 

 ratory, which could always be adjusted to about 70^ Fahr. 

 The rise was thus from 25^ to 30*^, which, with 4olb. of 

 water a minute, requited from 25 to 30 H.P. 



Before commencing the measurements everything 

 was adjusted, and the engines running at steady speeds 

 with constant load until the thermometer showed the tem- 

 perature to be steady. Then, at a signal, the counter was 

 put in gear and the water caught. The water thermometers, 

 and one showing the temperature of the laboratory, being 

 read at minute intervals over 15 or 30 minutes, when, on 

 a signal, the counter was removed and also the last bucket. 



The results of these tests were very consistent within 

 about 0'3 per cent, which was within the limits of accuracy 

 then aimed at. Trials with equal loads and different 

 speeds showed that the loss of heat by radiation was very 

 small, while those at the same speeds with different loads 

 showed that the balance was within the limits determined 

 by mechanical tests. 



In these trials the only correction was that for the 

 lubricating water which escaped from the brake bushes. 

 This was caught at each bush, and the temperature taken 

 so that the heat might be added, but this was seldom 

 more than 0*3 per cent. 



It is also to be noticed that in these trials the heat 

 lost or gained by conduction to or from the shaft was 

 included in the radiation. The brake being on an over- 

 hanging shaft, which extends no further than the outer 

 bush of the brake case, the only conduction is on the side 

 at which the shaft is continuous, where the brake shaft is 

 only some 4 inches from the brass of the shaft bearing. 

 The temperature of the brake on this side, which is 

 opposite to that at which the cold water enters, was kept 

 by the lubricating water at the temperature of the effluent 



