ON THE MECHANICAL EQUIVALENT OF HEAT. 
405 
1 
No. of 
i-evolntions 
of shaft. 
Work done. 
Heat 
generated, 
less 
losses 
due to 
terminals, 
conduc¬ 
tion, &c. 
Loss of 
heat by 
leakage 
of 
water. 
Terminal 
correc¬ 
tions. 
Differ¬ 
ence of 
tempera¬ 
ture 
between 
stuffing- 
box and 
bearing. 
Differ¬ 
ence of 
tempera¬ 
ture 
between 
brake 
and air. 
Means for 21 
accepted 
heavy trials 
17,817 
134,337,403 
171,510 
4 
- 1 
- 3-9 
140-5 
Means for 23 
accepted 
light trials 
17,832 
61,355,503 
77,710 
1 
— 7 
- 5-4 
141-5 
Differences j 
- lo 
72,981,900 
93,800 
3 
6 
1-5 
- 10 
(1) 
(•4) 
(3) 
(4) 
(5) 
(6) 
( 7 ) 
(8) 
A value of K can be obtained by dividing the difference of work in Column 3 by 
the uncorrected difference of beat in Column 4. This operation gives 
K = 778-06. 
The various corrections which this number requires are as follows :— 
I. Correction due to difference in number of revolutions of shaft between light and 
heavy trials. 
Since the difference in the number of revolutions is only 15, this correction, as 
previously indicated, when dealing with the balance of the brake, will be zero 
(par. 29). 
II. Correction due to loss by leakage of water from the brake. 
o 
This correction amounts to — = — 0-000032. 
93,800 
III. Correction due to terminal differences of temperature of the brake. 
This correction amounts to — —— 7 : = — 0*000064. 
93,800 
IV. Correction due to loss of heat by conduction along the sliaft. 
1 5 X 12 
This correction amounts to — jr = — 0 000192. 
9,o800 
V. Correction due to loss of heat by I’adiation. 
Assuming 9 for the value of the radiation constant, this becomes 
= + ssIto = + 
The total correction factor is therefore (1 — 0*000192), which gives as before 
‘K = 777-91. 
