250 
DE. H. T. BARNES ON THE CAPACITY FOE HEAT OF WATEE 
a different curve. The slope of the curve above 60° is very nearly the same as the 
well-known formula of Regnault, but the rate of increase is very much smaller. 
The following expression, which is very nearly a linear relation, holds between 
50° and 100° : 
S, = -99850 + -000120 (t - 55°) + ’00000025 (t - 55) 2 . 
These two formulae I have represented in the last table in column 3. They represent 
the variation of the specific heat of water very clearly with the exception of the 
rapid increase at 0°, and are entirely independent of the values assigned to my 
electrical units. They can be changed to fit a unit at any other temperature by 
simply changing the constant term. 
Since it would be a matter of great labour to determine the specific heat of 
superheated water, and since the variation curve of the specific heat shows no 
discontinuity as the boiling-point is reached at atmospheric pressure, this last formula 
may be said to hold with some claim to accuracy above 100° throughout the entire 
range covered by Regnault’s experiments. 
Comparison of Observed and Calculated Values. 
Temperature. 
Observed cl. 
Calculated cl. 
J observed. 
J. calculated. 
Series 
| 
I. February to March, 1899. 
1 
28-01 
- -00485 
- -00509 
4-1796 
4-1786 
29-09 
- -00469 
- -00517 
4-1803 
4-1783 
29-11 
- -00489 
- •00517 
4-1795 
4-1783 
29-21 
- -00499 
- -00519 
4-1790 
4-1782 
13-79 
- -00208 
- -00210 
4-1913 
4-1912 
17-69 
- -00309 
- -00328 
4-1870 
4-1862 
24-20 
- -00446 
- -00460 
4-1813 
4-1807 
34-46 
- -00561 
- -00545 
4-1765 
4-1771 
4-28 
+ -00330 
+ -00310 
4-2138 
4-2130 
Series II. January 6-22 
1899. 
22-16 
- -00413 
- -00425 
4-1827 
4-1822 
31-40 
- -00542 
- -00532 
4-1773 
4-1777 
'32-17 
- -00536 
- -00536 
4-1775 
4-1775 
41-02 
- -00540 
- -00539 
4-1773 
4-1774 
45-49 
- -00514 
- -00515 
4-1784 
4-1784 
49-68 
- -00531 
- -00480 
4-1777 
4-1799 
54-61 
- -00372 
- -00430 
4-1844 
4-1819 
59-80 
- -00341 
- -00370 
4-1849 
4-1845 
32-81 
- -00528 
- -00540 
4-1778 
4-1773 
30-54 
- -00555 
- -00528 
4-1767 
1 
4-1779 
