78 xMR. JOULE ON THE MECHANICAL EQUIV^ALENT OF HEAT. 
Table VL 
No. of experiment 
Total fall of 
Mean 
Difference be- 
tween mean of 
Temperature of apparatus. 
Gain or loss of 
and cause of change 
of temperature. 
weights in 
inches. 
temperature 
of air. 
columns 5 and 6 
and column 3. 
Commencement 
of experiment. 
Termination of 
experiment. 
heat during 
experiment. 
1 Friction 
1257*90 
46*362 
2*544 + 
46*837 
50*976 
4*139 
gain 
1 Radiation 
0 
46*648 
3*950 + 
50*976 
50*220 
0*756 
loss 
2 Radiation 
0 
47*296 
0*455 — 
46*730 
46*953 
0*223 
gain 
2 Friction 
1258*97 
47*891 
1*247 + 
46*953 
51*323 
4*370 
gain 
3 Friction 
1261*80 
47*705 
1*830 + 
47*352 
51*718 
4*366 
gain 
3 Radiation 
0 
48*547 
2*950 + 
51*718 
51*276 
0*442 
loss 
4 Radiation 
0 
47*825 
0*044 — 
47*756 
47*807 
0*051 
gain 
4 Friction 
1260*35 
48*385 
1*598 + 
47*807 
52*160 
4*353 
gain 
5 Radiation 
0 
48*323 
0*248 — 
48*009 
48*142 
0*133 
gain 
5 Friction 
1260*15 
48*833 
1*494 + 
48*142 
52*513 
4*371 
gain 
6 Friction 
1259*95 
48*049 
1*995 + 
47*902 
52*186 
4*284 
gain 
6 Radiation 
0 
48*632 
3*283 + 
52*186 
51*645 
0*541 
loss 
7 Radiation 
0 
50*385 
0*240 — 
50*053 
50*237 
0*184 
gain 
7 Friction 
1263*13 
51*018 
1*408 + 
50*237 
54*616 
4*379 
gain 
8 Friction 
1262*12 
48*385 
1*096 + 
47*249 
51*714 
4*465 
gain 
8 Radiation 
0 
49*199 
2*343 + 
51*714 
51*371 
0*343 
loss 
9 Friction 
1257*20 
49*721 
2*495 + 
50*160 
54*273 
4*113 
gain 
9 Radiation 
0 
50*338 
3*643 + 
54*273 
53*689 
0*584 
loss 
10 Radiation 
0 
48*439 
0*821 + 
49*271 
49*250 
0*021 
loss 
10 Friction 
1258*70 
49*690 
2*282 + 
49*877 
54*067 
4*190 
gain 
Mean Friction ... 
Mean Radiation... 
1260*027 
0 
1*7989 + 
1*6003 + 
4*303 gain 
0*2096 loss 

o 
3 
4 
5 
6 
7 
From the above Table, it appears that there was a thermornetrical effect of 0°'20101 
for each degree of difference between the temperature of the laboratory and that of 
the apparatus. Hence 4°-303 + 0°‘2096 + 0°’03992 = 4°‘55252, will be the proximate 
mean increase of temperature. The correction, owing to the mean temperature 
of the mercury in the friction experiments appearing 0°‘07625 too low in the table, 
will be 0°’01533, which, added to the proximate result, gives 4°‘56785 as the true 
mean increase of temperature. 
The capacity of the apparatus was obtained by experiments made in precisely the 
same manner that I have already described in the case of the mercurial apparatus 
for fluid friction. Their results are collected into the following Table. 
