366 
On the Measure of Temperature, 
[Bee. 
This table evidently leads to the same truth as the preceding To show that it 
extends to all the gases, whatever may be their nature and their density, we shall 
here, give the results of experiments made on carbonic acid, under a ptessure of 
0 m ,72, and on common air, rarefied to the pressure 0 m ,36. 
1. With Carbonic Acul Gas. 
Excess of temp. 
Rates of cooling due solely to the contact of the gas. 
of the therm, 
over the sur- 
Pressure 0 m ,72. 
Pressure 6 m ,72. 
Pressure 0 m ,72 
Pressure 0 m ,72 
rounding air. 
Temp. 20°. 
Temp. 40°. 
Temp. 60°. 
Temp. 80°. 
200° 
5°, 25 
5°, 17 
• • • • 
• • • • 
180 
4 ,57 
4 ,63 
4°, 52 
• • • • 
160 
4 ,04 
4 ,06 
3 ,97 
4,10 
140 
3 ,39 
3 ,39 
3 ,34 
3,43 
120 
2 ,82 
2 ,80 
2 ,79 
2,83 
100 
2 ,22 
2 ,18 
2 ,21 
2,20 
2. With Common Air rarefied. 
Excess of temp, 
of therm, over 
that of sur- 
rounding air. 
Rates of cooling due solely to the contact of the gas. 
Pressure O'" ,36. 
Temp. 20°. 
Pressure 0 IU ,3G. 
Temp. 40 . 
Pressure 0™, 36. 
Temp. 60°. 
Pressure 0 m ,36 
Temp. 80°. 
20 
4° ,01 
4°, 10 
• • • • 
• • • • 
180 
3 ,52 
3 ,50 
3°, 55 
• • • • 
160 
3 ,03 
2 ,99 
3 ,04 
3°, 09 
140 
2 ,62 
2 ,57 
2 ,62 
2 ,66 
120 
2 ,12 
2 ,16 
2 ,14 
2 ,15 
100 
1 ,69 
1 ,71 
1 ,67 
1 ,73 
From all these comparisons, we may deduce the following law . 
7 he rate of cooling of any body , os due solely to the contact of a gas, depends for 
the same excess of temperature, on the density and temperature of the fluid ; but this 
dependence is such, that the rate of cooling remains the same if the density and the 
temperature of the gas change, so that the elasticity remains constant . 
In our researches, then, on the law of cooling in gases, we have only occasion to 
consider elasticity. It is then the influence of this property which it is necessary 
to determine. . , , , . 
To obtain it, we have determined successively, for each gas, and at different 
elasticities, the rates of cooling, corresponding to the same excess of temperature. 
We shall only give such account of these experiments as may be sufficient to 
establish the law to which we have been led. 
Let us begin with air. 
The following table contains the rates of cooling, due solely to the contact of air 
under the pressures 0 m ,72 0 m ,36 0 m ,18 0 m ,09 0 ni ,045, that is to say, under pres- 
sures which are as the numbers 
l I 2 l l 
<2* 4-i 8* 1 6* 
Excess of the 
therm, over the 
temp, of the sur- 
rounding- air. 
Rates of cooling due solely to the contact of the gas. 
Pressure 
0 m ,72. 
Pressure 
011,36. 
Pressure 
0 m ,lS. 
Pressure 
0 m ,09. 
Pressure 
0 m ,045. 
200* 
5°, 48 
4°, 01 
2°, 95 
2°, 20 
1°,59 
180 
4 ,75 
3 ,52 
2 ,61 
1 ,90 
1 ,37 
160 
4,17 
3 ,03 
2 ,21 
1 ,62 
1 ,20 
140 
3 ,51 
2 ,62 
1 ,91 
1 ,40 
1 ,02 
120 
2,90 
2 ,12 
1 ,57 
1,15 
0 ,84 
100 
2 ,27 
1 ,69 
1 ,23 
0 ,90 
0 ,65 
80 
1,77 
1 ,29 
0 ,96 
0,70 
0 ,52 
60 
1 ,23 
0 ,90 
0 ,65 
0,48 
0 ,35 
40 
0 ,75 
• • • • 
* • * • 
• • • • 
• • • • 
20 
0 .32 
• • • • 
• • • • 
• • * • 
