Manchester Me uioii's, VoLxlzi. {i^g^), No. ^. 37 



in the plan suggested above, the power available for the 

 purposes of the research enabled me to deal, in trials of 

 one hour's duration, with quantities approaching the 

 following values : — 



Revolutions, 18,000. 



Total work done, 135,000,000 ft.-lbs. 



Total weight of water raised iSo'^F., 96olbs. 



Total apparent heat generated, 170,000 B.T.U. 

 In quantities so large as these, some of the small errors 

 inevitable to all physical experiments became quite or 

 nearly negligible. 



2. Arrangement of the apparatus. 



Before the experiments could be begun it was 

 necessary to specially arrange the line of piping supplying 

 water to and discharging it from the brake. The course 

 taken by the water in the apparatus as completed was 

 as follows i^Fig. 6) : — 



From the mains in the laboratory it was forced by a 

 centrifugal circulating pump through a length of about 

 200ft. of ^in. diam. composition pipe, immersed in a 

 well-stirred mixture of ice and water, with the object of 

 cooling it to 32°F. From this pipe the water flowed into 

 a glass tube carrying the thermometer which indicated 

 the temperature of supply to the brake, the whole stem of 

 the thermometer being immersed in the water and the 

 readings being taken through the glass walls of the 

 chamber. From this chamber the water was delivered 

 through a flexible rubber pipe to the brake. Here its 

 temperature was raised to 2I2°F. before being forced 

 through a second rubber pipe into the fixed discharge 

 pipe, which carried a second thermometer jackctted like 

 the former one with the water whose temperature was 

 required. The water was then cooled by passing through 

 an iron condenser of the ordinary chemical pattern, and 



