40 Reynolds and Moorby, Equivalent of Heat, 



3rd. — The regulating valve controlling the flow of 

 water from the brake. 



Some leakage occasionally occurred at the shaft 

 stuffing-box. This was all caught in the later trials, and 

 the heat generated in it per lb. was assumed to vary as 

 difference of the temperatures of the stuffing-box cover 

 and of the water in the supply pipe. 



The second stuffing-box worked absolutely dry. 

 Leakage always occurred at the regulating cock. This 

 consisted of hot water, and a special device was made to 

 catch it so as to ensure no loss by evaporation. The 

 water thus caught was weighed with the main stream 

 which had entered the tank, and credited with the full 

 rise of temperature between the supply and discharge 

 pipes. A fourth working joint in the envelope was at the 

 point where the discharge pipe emptied itself into the 

 tank. A determination of the loss that might occur in 

 the end of the discharge pipe and tank was- made by 

 pumping the water continuously for an hour up from the 

 tank, and back to it through the discharge pipe, which 

 had been disconnected from the brake for the purpose. 

 The loss was found to be very nearly J4^1b. in all trials, 

 and, since it would be eliminated almost entirely on the 

 difference of heat, it was neglected altogether. 



A further correction was often necessary to the 

 apparent heat obtained on account of the change in tem- 

 perature of the brake itself, together with its water content, 

 during a trial. The amount of contained water varied 

 with the speed of revolution. Accordingly a curve was 

 plotted giving, for different speeds and loads, the thermal 

 equivalents of the brake and contents. 

 At 300 revs, and 1200 ft.-lbs. this was 57*6 lbs. of water. 



» 600 „ „ 54-6 



The gain or loss of heat by the brake was added to or 

 subtracted from the apparent heat obtained. 



