SPECIFIC HEAT OF GASES. 
141 
meter. By repetition of these means with the quantity of gas 
required to fill one of the gazometers, it was possible to keep 
up a current of hot gas through the calorimeter for several 
hours*. 
The apparatus was so disposed that the calorimeter was in a 
separate room, the door of which was seldom opened, and in 
which, consequently, the air not being agitated, preserved 
a temperature varying very little. 
Section III. 
Means to discover the Qnantily of Ilent which is lost by the 
Current of Gas in passing through the Calorimeter. 
In heating the gas by the process described above, it is evi- 
dent, that whether it is used at the temperature of boiling 
' water, or whether it remains a little below it, it will never- 
I theless acquire a constant temperature. It seems easy, on a 
1 first view., to determine that temperature by placing a ther- 
iinometer in the centre of the tube through which the gas 
j passes ; but on a little attention we shall find, that the ther- 
imometer thus placet! would indicate a temperature lower than 
that of the current. In fact, the outside of the tube being 
•always colder than the current of gas which passes through the 
. centre, must consequently act by radiation on the bulb of the 
thermometer, and lower its temperature. When a thermo- 
meter, with the bulb gilt and polished, has been placed in the 
centre of the tube, and which has been less influenced by the 
•radiation, it has been kept above a degree higher than the 
(common thermometer. This fact evidently proves the influ- 
,ence of the coating, and consequently the difficulty of deter- 
mining, by means of a thermometer, the temperature of the 
I current passing through the tube. 
This difficulty in appreciating the temperature of the current 
• Tbc ori»iiial IMcmoir, in the Annales dc Chimic, indicates the 
meanK we adopted to preveut any alteratiou in the gas during seve* 
‘ verai hours experiment. 
of 
Metliod of 
discoveiinc 
the liciit lu»t 
in passing 
through the 
caloiimcter. 
