ON THE MECHANICAL EQUIVALENT OF HEAT. 
391 
at various speeds by suddenly stopping the engine when running at any given speed, 
simultaneously shutting off the water supply to the brake, and afterwards draining 
off and weighing the water shut in. 
The results are shown in the annexed curves. 
Fig. 10. 
27 
26 
25 
k 
I 
23 
^22 
% 
27 
20 
C 
(s' ' 
' 
< 
• \ 
62 
6/ 
60 
59 
I 
-I 
I- 
.5/ 
I 
66 
55 
54 
7/0 730 /SO 200 2/0 220 230 240 250 260 270 280 290 300 
/tei/o/uC/oTis perm/nc/Oe. 
Curves stowing water contained by aud water 'equivalents of brake and contents at varying speeds. 
The weight of brass in the brake is 363 lbs. Taking 0-094 for its specific heat, 
the water equivalent is 34-6 lbs. 
To obtain a scale of weights representing the water equivalents of the brake at 
different speeds, we have to add 34*6 to the weights of water contained at the 
different speeds. 
This scale is given at the right of the curves just alluded to (see above). 
A correction to the heat obtained is now very easily deduced. 
Let %v^^ ■=■ water equivalent of brake at commencement of trial. 
= „ „ end „ 
q = temperature of water in discharge pipe at commencement of trial. 
,, ,, ,, end ,s 
Therefore, additional heat generated in the brake = this quantity 
is added to the heat already calculated as generated in the water. 
The speed indicator wbich was used in the determination of the number of revo- 
