316 
On the Measure of Temperature, 
[Oct. 
The first of the following tables contains the rates of cooling of mercury and 
water ; the second gives the comparison between mercury and absolute Alcohol ; the 
third between mercurv and concentrated sulphuric Acid. 
Excess of Tem- 
perature. 
Rate of Cooling 
with Mercury. 
Rate of Cooling with 
Water. 
Ratio of these Rates. 
60° 
3,03 
1,39 
0,458 
50 
2,47 
1,13 
0,452 
40 
l,s9 
0,85 
0,4.0 
30 
3,36 
0,62 
0,456 
Excess of Tem- 
Rate of Cooling 
Rate of Cooling with 
Ratio of these Rates. 
perature. 
with Mercury. 
Alcohol. 
40 
1,89 
1,50 
0,798 
30 
1,36 
1/9 
0,801 
20 
0,87 
0,69 
0,794 
Excess of Tem- 
perature. 
Rate of Cooling 
with Mercury. 
Rate of Cooling with 
Sulphuric Acid. 
Ratio of these Rates. 
60 
3,03 
1,97 
0.650 
50 
2,47 
1,59 
0,649 
40 
1,89 
1,22 
0,646 
30 
1,36 
0,89 
0,654 
The ratios in the last column of each of these tables show, that the law of cooling 
is the same for each of these four liquids ; the small variations observable, appearing 
evidently to be the effect of uncertainty of observation ; for they might be made to 
disappear, by altering the rates of cooling only one hundredth of a degree. 
Now if liquids so different in tlieir nature, their density, their fluidity, present 
such perfect similarity in the laws of cooling, we may generalise this result, and 
say, that a liquid mass, such as we have used, whatever may be its nature, must 
cool, agreeably to the elementary law we are investigating. 
There still remained the shape of the vessel to he examined. We first compared 
the cooling of two spheres, one of glass, the other of tinned iron, both filled with 
water. The radius of the latter exceeded, by a small quantity, that of the former, 
Excess of Tem- 
perature. 
Rate of Cooling of 
the Glass Sphere. 
Rate of Cooling of 
the Tinned Sphere. 
Ratio of these Rates. 
60 
1,39 
0,90 
1,54 
50 
1,13 
0,73 
1,55 
40 
0,85 
0,54 
1 ,57 
30 
0,62 
0,38 
1 ,63 
20 
0,37 
0,21 
1,76 
Here the ratios inserted in the last column vary always in the same direc m » 
and show that the law of cooling is more rapid for the vessel of tinned plate 
for that of glass. Mr. Leslie has arrived at the same conclusion, which he has gen 
ralized, by admitting that the law changes with the nature of the body, and t ,at 1 
more rapid as these bodies radiate less. This proposition is true only m t a P 
of the thermometric scale which Mr. Leslie has confined himself to in his exp . 
ments ; but by a very remarkable circumstance, a contrary effect is produce 1 
higher temperatures. So that when we compare the laws of cooling o. two 0 ’ . 
having different surfaces, that law which is the more rapid in the lower par 
