328 Dulong and Petit on the Measure of Teniperatures, [Mar, 
1. The law, according to which the velocity of cooling due to 
the sole contact of hydrogen varies with the excesses of temperature, 
‘ ds the same, whatever be the elasticity of the gas. 
2. The cooling power of hydrogen decreases in a geometrical 
progression, whose ratio is 1-301, when its elasticity diminishes in 
a geometrical progression, whose ratio is 2. 
fe obtained the same consequences for carbonic acid and 
olefiant gas. This may be easily verified in the two following 
tables, arranged for each of these gases as the table given above 
for hydrogen. 
Velocities of 
Exgcess of tems cooling dueto/Ditto. Pres-/Ditto. Pres- 
perature Sipappaie rs u f 
above the gas. catban edt sure 0°36 m. | sure 0-18 m. 
eel 
Ditto. Ditto. 
Pressure | Pressure 
0-09 m. 0-045 m. 
——— 
ee 
200° 5:25° 364° 2°56° 1-799 1:25° 
180 4°57 3°22 2°25 1°56 1-09 
160 4°04 2°80 1:97 1-37 0:95 
440 3°39 2°38 1°65 117 0-80 
120 2°82 1:97 1°36 0°95 0°6T 
100 2°22 1°55 1-08 0°16 052 
80 1-69 117 0 82 0:57 0:40 
60 1:18 0°82 0°57 0°40 0°28 
i end 
Velocities of 
cooling due tolnitto, Pres-|Ditto. Pres- pees Ditto. 
Excess of tem- 
perature o 
the contact of, Pressure | Pressure 
bea above olefiant gas. sure 0:36 m. | sure 0°18m. 0°09 m. 0-045 m. 
= Pres. 0°12 m. 
200° TALS 518° 8-649 ect 1-84° 
180 6°45 4°57 BE ~ 4°22 1°59 
160 5°41 3:85 2°12 1°89 1°34 
140 4°70 3°31 2°35 1:63 118 
120 3°84 2°16 1°92 1°35 0:96 
100 3:12 2°21 1-55 1:08 0°18 
80 2°34 162 1-15 0°79 0-62 
Mean of all these Ratios. 
For carbonic acid ........+..-6. = 1°43] 
For olefiant gas.......secaseee. = L415 
From all that precedes, we may draw the following conse- 
quences : \ 
1. The losses of heat due to the contact A a gas increase with 
the excess of temperature, according to a law which remains the 
same whatever be the elasticity of the gas. 
2. The cooling powers of the same gas vary in geometrical pro- 
gression, while the elasticities vary in geometrical progression ; 
and if we suppose the ratio of this second progression to be 2, the 
ratio of the first progression will be 1:366 for air; 1:301 for 
hydrogen; 1°341 for carbonic acid; and 1:415 for olefiant gas. 
