78 THE DYNAMICAL THEORY OF GASES. 



Since all the quantities which enter into the expression for C are constant 

 except p., the conductivity is subject to the same laws as the viscosity, that is, 

 it is independent of the pressure, and varies directly as the absolute tempera- 

 ture. The conductivity of iron diminishes as the temperature increases. 



Also, since y is nearly the same for air, oxygen, hydrogen, and carbonic 

 oxide, the conductivity of these gases will vary as the ratio of the viscosity 

 to the specific gravity. Oxygen, nitrogen, carbonic oxide, and air will have 

 equal conductivity, while that of hydrogen will be about seven times as great. 



The value of y for carbonic acid is 1'27, its specific gravity is JJ- of 

 oxygen, and its viscosity ^ of that of oxygen. The conductivity of carbonic 

 acid for heat is therefore about $ of that of oxygen or of air. 



