318 
PROFESSOR 0. REYNOLDS AND MR. W. H. MOORBY 
This rise was such as admitted of the temperature of the brake being the same as 
tliat of tlie laboratory, which could always be adjusted to about 70° Fahr., so that 
the rise was from 25 to 30 degrees. Tliis, with 40 lbs. a minute, required from 
25 to 30 h.p. 
Before commencing the actual trial everything was adjusted, and the eno-ines 
running with steady load and steady speed until the thermometer showed the heat 
to be steady at the desired temperature, then, at a signal, the counter was put in 
and the water cauoht, each of the thermometers, and one giving the temperature 
of the laboratory, being then 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 limit of accuracy then aimed at. 
Trials with equal loads and different speeds showed that the loss by radiation nns 
very small, while those at the same speed with different loads showed 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 bearing, and the tempe¬ 
rature taken so that the heat might be added, this being seldom more than 
3 per cent. It may also be noticed that in these trials the heat lost or gained by 
conduction to or from the shaft was included in the radiation. As the brake is 
on an overhanging shaft which extends no farther than the outer bush of the brake 
case (Plate 3), the only conduction is on the side at which the shaft is continuous, 
where the brake bush is only some 4 inches from the brass of the shaft bearino-. As 
*/ 
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 at which 
the water left the brake, and this was at temperature of the laboratory, there would 
be 210 cause of conduction unless the friction of the shaft in its bearing caused its 
temperature to rise above that of the laboratory. When the lubrication was good 
this was small, although on one or two occasions it made itself felt. 
The Idea of Raising the Temperature from 32 to 212. 
11. These tests became an annual exercise in the laboratory, and a very instructive 
exercise. But, as the subject—the value of the equivalent—was attracting much 
attention, the desire to obtain measures of it from these trials, by those engaged in 
them, resulted in Mr. T. E. Stanton, M.Sc., then Senior Demonsti’atoi’, effecting, 
for his own satisfaction, a comparison of the scales of the thermometers used m 
the expeiknents with a thermometer used in the Pliysical Laboratory, which 
had been compared ivith the air thermometer, and introduced these coi’rections into 
the results of the trials, which so gave values very close to what might be expected. 
I could not see however that deteianinations made with thermometers so corrected 
