MR. JOULE ON THE MECHANICAL EQUIVALENT OF HEAT. 
81 
Table VIII. 
No. of experiment 
Total fall of 
Mean 
Difference be- 
tween mean of 
columns 5 and 6 
and column 3. 
Temperature of apparatus. 
Gain or loss of 
and cause of change 
of temperature. 
weights in 
inches. 
temperature 
of air. 
Commencement 
of experiment. 
Termination of 
experiment. 
heat during 
experiment. 
1 Friction 
1281-07 
4T404 
6-852 + 
4T494 
49*018 
1-524 
gain 
1 Radiation 
0 
48-003 
0-998 -f- 
49-018 
48-984 
0-034 
loss 
2 Radiation 
0 
48-269 
0-702 + 
48-984 
48-958 
0-026 
loss 
2 Friction 
1280-74 
48-516 
1-189 + 
48-958 
50-452 
1-494 
gain 
3 Radiation 
0 
49-003 
0-133 — 
48-812 
48-928 
0-116 
gain 
3 Friction 
1285-10 
49-728 
0-022 + 
48-928 
50-572 
1-644 
gain 
4 Friction 
1283-89 
50-138 
1-172 -h 
50-572 
52-049 
1*477 
gain 
4 Radiation 
0 
50-408 
1-581 + 
52-049 
51-929 
0-120 
loss 
5 Friction 
1282-45 
46-798 
0-558 + 
46-554 
48-159 
1-605 
gain 
6 Friction 
1281-29 
47-296 
1*571 + 
48-159 
49-576 
1-417 
gain 
5 Radiation 
0 
47-535 
1-929 + 
49-576 
49-353 
0-223 
loss 
6 Radiation 
0 
47-651 
1-607 + 
49-353 
49-164 
0-189 
loss 
7 Radiation 
0 
46-261 
0-298 — 
45-880 
46-047 
0-167 
gain 
8 Radiation 
0 
46-748 
0-617 - 
46-047 
46-215 
0-168 
gain 
7 Friction 
1276-07 
46-810 
0-978 + 
47-022 
48-554 
1-532 
gain 
8 Friction 
1275-17 
47-366 
1-883 + 
48-554 
49-945 
1-391 
gain 
9 Radiation 
0 
46-771 
0-271 — 
46-425 
46-575 
0-150 
gain 
9 Friction 
1276-95 
47-126 
0-258 + 
46-575 
48-194 
1-619 
gain 
10 Friction 
1276-84 
47-238 
1-655 -f 
48-194 
49-593 
1-399 
gain 
10 Radiation 
0 
47-335 
2-142 + 
49-593 
49-361 
0-232 
loss 
Mean Friction ... 
Mean Radiation... 
1279*957 
0 
1-0138 -f 
0-764 + 
1-5102 gain 
0-0223 loss 
1 
2 
3 
4 
5 
6 
7 
From the above Table, it appears that the effect of each degree of difference between 
the temperature of the laboratory and that of the apparatus was 0°’] 591. Hence 
l°'5102+0°'0223+0°'03974 = l°’37224, will be the proximate heating effect. To this 
the addition of 0°'00331, on account of the mean temperature of the apparatus in the 
friction experiments having been in reality 0°‘02084 higher than appears in the Table, 
gives the real increase of temperature in the experiments at 1°'57555, which, in the 
capacity of 11796 07 grs. of water, is equivalent to 1° in 2‘65504 lbs. of water. 
The leaden weights amounted to 137326 grs., from which 1040 grs., subtracted 
for the friction of the pulleys, leaves 136286 grs. Tlie velocity of descent, which 
was in this case much more easily regulated than when the heavier M’^eights were 
used, was T9 inch per second. Twenty impacts with this velocity indicate a loss 
of fall of 0‘094 inch, which, subtracted from 1279'957, leaves 1279*863 inches as the 
corrected height from which the weights fell. 
The above height and weight are equivalent to 2076*517 foot-lbs., to which the addi- 
tion of 1*189 foot-lb. for the elasticity of the string, gives 2077'706 foot-lbs. as the 
MDCCCL. M 
