13G JAMES CLERIC MAXWELL 



under tho action of gravity, the equilibrium of tem- 

 perature between two gases, and the distribution of 

 temperature in a vertical column. These results are, 

 as he states, independent of the law of force between 

 the molecules. The dynamical causes of ditVusion 

 viscosity and conduction of heat are dealt with, and 

 these involve the law of force. 



It follows also from the investigation that, on the 

 hypotheses assumed as its basis, if two kinds of gases 

 bo mixed, tho dillercnce between tho average kinetic 

 energies of translation of tho gases of each kind 

 diminishes rapidly in consequence of the action 

 between tho two. Tho average kinetic energy of 

 translation, therefore, tends to become the same for 

 each kind of gas, and as before, it is this average 

 energy of translation which measures tho tem- 

 perature. 



A molecule in the theory is a portion of a gas 

 \vhich moves about as a single body. It may be a 

 mere point, a centre of force having inertia, capable 

 of doing work while losing velocity. There may 

 bo also in each molecule systems of several such 

 centres of force bound together by their mutual 

 actions. Again, a molecule may l>e a small solid 

 body of determinate form; but in this case we must, 

 as Maxwell points out, introduce a new set of forces 

 binding together the parts of each molecule: we must 

 have a molecular theory of the second order. In any 

 case, tho most general supposition made is that a 

 molecule consists of a series of parts which stick 

 together, but are capable of relative motion among 

 each other. 



