THE MECHANICAL EQUIVALENT OF HEAT. 
451 
Experiments 79 and 80. —The simple Hooke’s joint was now replaced by a light 
ring of wire, which passed through holes in the stirring rod and the revolving shaft. 
o- = -000272 
p = -000374 
Q = -0136. p = *44 millun. 
^ J 19. 
It thus appeared that both a and p had resumed their former values. 
Experiments 81 and 82.—These two experiments were intended to be the first 
pair of a series. On commencing J 20, the same evening (September 4), it was 
discovered that the coil in the calorimeter had become loose. The calorimeter had, 
in consequence, to be taken to pieces, and a week elapsed before we were able to 
resume our J determination. These two experiments are consequently of no use, but 
they are interesting as showing the kind of accuracy obtainable. 
W = 140-270. 
o- = -000439. 
V = -000578. 
Q = -0130. p = -36 millim. 
Experiments 83 to 93.—After Experiment 82 a marked difference is observable in 
the value of cr. Between September 4 and 10 the calorimeter had been thoroughly 
cleaned, and all gutta-percha surfaces removed from its interior. The “ throw ” of 
the stirrer was evidently improved, and as a consequence the value of cr was raised. 
The series of J Experiments (Series II., J 20 to 34), performed after this change, 
are so much superior to their predecessors that we base our conclusions almost 
entirely upon them. We feel it right, therefore, to give more particulars concerning 
their “ non-electrical supply ” determinations than we have considered necessary in the 
case of Series I. (J 1 to 19). The following table is a summary of the “ stirring 
experiments ” used in the reduction of J 20 to 25. 
Table XXIII.—W = 139-776. 
Date. 
Range E„. 
Range C. 
Time. 
Rate. 
Range 
Time ’ 
Rate 
correction 
X 106. 
Rise at 
rate 30. 
Mean 
tem¬ 
perature 
C. 
Sept. 10 . 
292-5-30;-5 
•384 
752-05 
29-93 
•000510 
+ 3 
•000513 
19-260 
55 
10 . 
87-5-127-5 
•973 
1173-43 
30-35 
•000829 
- 18 
•000811 
14-476 
)> 
10 . 
292-5-.307-5 
•384 
746-75 
.30-07 
•000514 
- 4 
•000510 
19-260 
)5 
11 . 
292-5-307-5 
•384 
7.33-6 
.30-18 
•000523 
- 9 
•000514 
19-260 
11 . 
292-5-.307-5 
•384 
753'22 
29-96 
•000510 
+ 2 
•000512 
19-260 
11 . 
442-5^52-5 
•263 
899-23 
30-31 
•000293 
- 13 
•000280 
23064 
13 . 
292-5-307-5 
•384 
72.3'05 
30-20 
•000522 
- 10 
•000512 
19-260 
95 
13 . 
87-5-127-5 
•973 
1168-85 
30-39 
•0008.32 
- 20 
•000812 
14-476 
59 
13 . 
442-5-4.52-.5 
•263 
890-65 
30-30 
•000296 
- 15 
•000281 
23-064 
3 M 2 
