190 New experimental Researches 
at our ordinary atmospherical heats, it possesses the greatest ca~) 
pacity for caloric, small variations in its temperature ‘give it a 
great modifying power over the circumambient air. Although 
the doctrine of final causes be no safe guide to'the discovery of 
unknown truths, yet when’ it concurs with experiment, we may 
deem it an agreeable confirmation. This is finely illustrated by 
Count Rumford’ s speculations on the maximum density of water 
being placed several degrees above its point of congelation; a 
fact which does not hold with regard to any other homogeneous 
liquid. 
If the specific heat of water, then, diminish as its temperature 
advances from the freezing to the boiling point, an interval of 
10° near 32° will contain more calorie than ten degrees near 
122°, anid still more than the same intervals near 212°. On this 
principle we can readily account for the results obtained by Mr. 
Dalton, in mixing with water at different temperatures a known 
proportion of ice; though it is remarkable that this able chemist 
did not see in them any thing inconsistent with his own opposite 
views upon specific heat. 
‘* 176°5 expresses the number of degrees of temperature, such 
as are found between 200° and 212° of the old or common 
seale, entering into ice of 32°, to convert it into water of 32°; 
150° of the same scale suffice, he says, for the same effect, be- 
tween 122° and 130°: and between 45° and 50°, 128° are 
““ adequate to the conversion of the same ice into water. These 
three resulting numbers (128, 150, 176°5) are nearly as 5,6, 7. 
Hence it follows, that as much heat is necessary to raise water 
5° in the lower part of the old scale, as is required to raise it 7° 
in the higher, and 6° in the middle *.”’ 
Mr. Dalton, instead of adopting the obvious conclusion, that 
the capacity of water for heat is greater at lower than it is at 
higher temperatures, and that therefore a smaller number of de- 
grees of the former should melt as much ice as a greater nnmber 
of the latter, ascribes the deviation denoted by these numbers, or 
their differences, to the gross errors of our thermometric gradua- 
tion; which he considers so excessive, as not only to equal, but 
greatly to overlalance the real increase in the specific heat of 
water; which left to its own operation, would have produced 
opposite experimental results. 
' That our thermometric scale has no bal prodigious deviation 
from truth, or uniformity of indication, { conceive to be fully. 
established ; and therefore the only legitimate inference from these 
very experiments of Mr. Dalton, is the decreasing capacity of 
water with the increase of its temperature. 
* New System, vol. i. p. 53. 
It 
