MR. JOULE ON THE MECHANICAL EQUIVALENT OF HEAT. 
79 
Table VII. 
Iso. 
Corrected temperature 
of water. 
Gain of heat by 
the water. 
Corrected temperature 
of apparatus. 
Loss of heat by 
the apparatus. 
Commencement 
of experiment. 
Termination 
of experiment. 
Commencement 
of experiment. 
Termination 
of experiment. 
1 
45-535 
4^305 
i-770 
71-112 
4^421 
23-691 
3 
46-210 
47-937 
1-727 
71-292 
48-073 
23-219 
3 
47-334 
49-023 
1-689 
71-454 
49-151 
22-303 
4 
49-007 
50-555 
1-548 
71-152 
50-632 
20-520 
5 
47-895 
49-498 
1-603 
71-249 
49-636 
21-613 
6 
48-784 
50-357 
1-573 
71-445 
50-460 
20-985 
7 
50-323 
51-757 
1-434 
70-793 
51-808 
18-985 
8 
47-912 
49-525 
1-613 
71-253 
49-653 
21-600 
9 
48-449 
50-013 
1-564 
70-798 
50-083 
20-715 
10 
49-836 
51-337 
1-501 
71-356 
51-375 
19-981 
11 
46-870 
48-559 
1-689 
71-026 
48-657 
22-369 
12 
48-562 
50-151 
1-589 
71*291 
50-199 
21-092 
Mean... 
1-60833 
21-42275 
By adding 0°’00071 and 0°‘0141, the loss and gain of Table IV. reduced to the 
surfaee of the solid-friction apparatus, to the above mean results, we have a gain of 
1°’60904 by the water and a loss of 21°‘43685 by the apparatus. The capacity of the 
can of water was in this instance as follows ; — 
Water 155824 grs. 
Copper can as water 1486 grs. 
Thermometer and stirrer as ditto 1 18 grs. 
Total . . . 157428 grs. 
Hence 21 :^ 35 ^ X 157428= 1 181 6'47, will be the capacity of the apparatus as tried. 
By applying the two corrections, one additive on account of the absence during the 
trials of 300 grs. of mercury, the other subtractive on account of the capacity of the 
thermometer C and suspending wire, we obtain 1 1796'07 grs. of water as the capacity 
of the apparatus during the experiments. 
The temperature 4°'56785 in the above capacity, equivalent to 1° in 7'69753 lbs. 
of water, was therefore the mean absolute quantity of heat evolved by the friction of 
cast iron. 
The leaden weights amounted to 406099 grs., from which 2857 grs., subtracted on 
account of the friction of the pulleys, leaves 403242 grs. as the pressure applied to 
the apparatus. 
Owing to the friction being in the simple ratio of the velocity, it required a good 
deal of practice to hold the regulating lever so as to cause the weights to descend to 
