CONTINUOUS ELECTRIC CALORIMETRY. 
101 
tain, and are for this reason given only to the nearest part in 10,000. The platinum- 
scale correction is given for comparison in the last line of the table. 
Table V.—Corrections (Parts in 10,000) to be added to reduce the Value of the 
Specific Heat of Water from the Nitrogen to the Hydrogen Scale. 
Temperature, Centigrade .... 
0° 
10° 
20° 
30° 
40° 
50° 
o 
o 
o 
o 
so 
80° 
90° 
100° 
Chappuis, formula (2). 
+ 6 
+ 5 
+ 3 
+ 1 
-1 
-3 
-4 -4 
- 2 
+ 1 
+ 6 
,, corrected. 
+ 6 
+ 4 
+ 3 
+ 1 
+ 0 
- 1 
-2 -2 
-2 
— 2 
- 2 
Joule-Thomson, constant-volume, 
100 centims. 
+ 4 
+ 3 
+ 2 
+ 1 
+ 0 
-0 
- 1 - 1 
-2 
-2 
-3 
Joule-Thomson, constant-pressure, 
76 centims. .. 
+ 7 
+ 5 
+ 3 
' +2 
+ 1 
-1 
-2 -2 
-3 
-4 
-5 
Platinum scale correction by differ- 
ence-formula (1). 
+ 150 
+ 120 
+ 90 
+ 60 
+ 30 
0 
-30 -60 
-90 
-120 
- 150 
It will be observed that the correction in any case is very small, and that the 
uncertainty of the correction is nearly as large as the correction itself. A change of 
nearly 1 in 1000 in the correction at 100° is produced, if we adopt the “ corrected” 
results of Chappuis instead of the table taken by Griffiths. On the whole, as the 
difference-formula (l) was obtained by comparison with a constant-pressure air- 
thermometer at 76 centims., we shall probably be most nearly correct if we apply the 
corrections calculated from the observations of Joule and Thomson for air under the 
same conditions. The corrections thus obtained do not differ materially from those 
applied by Griffiths (they agree to 1 in 5000), except at 90° and 100°, where they 
differ by 5 and 11 in 10,000 respectively. I have therefore assumed the corrections 
calculated from Joule and Thomson in reducing the results to the hydrogen scale in 
Table XII., Section 37. 
The value 1'54 for the difference-coefficient already referred to was obtained by 
Harker and Chappuis with a constant-volume nitrogen-thermometer at 56 centims. 
initial pressure. The corrections for this case can be calculated from the observations 
of Joule and Thomson by reducing those for the constant-volume thermometer given 
in Table IV. in proportion to the initial pressure, namely, in the ratio 56 to 100. It 
happens that if our results are reduced by employing Chappuis and Harker’s value 
of the difference-coefficient, 1*54, and are then corrected to the hydrogen scale by 
applying the correction for the constant-volume nitrogen-thermometer at 56 centims., 
the results are identical with those obtained by using the difference-coefficient, 1*50, 
and then applying the correction for the constant-pressure air-thermometer. This 
agreement, however, is not really so satisfactory as it appears at first sight, because, 
according to the theory on which it is based, the correction to the hydrogen scale 
does not follow the same function as the difference-formula, and the difference in the 
