THE RATIO OF THE SPECIFIC HEATS OF 



GASES. 



THE Kinetic Theory of Gases is making little progress 

 at present, for want of information regarding the 

 nature and relations of the parts of a molecule. The laws 

 of Boyle, Charles and Avogadro have been fairly com- 

 pletely explained without this knowledge, as have also the 

 main facts concerning diffusion and viscosity, but wherever 

 temperature changes come in there begin to be difficulties. 

 The way in which the viscosity coefficient of a gas varies 

 with the temperature has not been explained, because we 

 do not know the law of force between two molecules, and 

 work on the specific heat is rendered nugatory from our 

 ignorance of the nature of the atoms and their relations 

 to each other. 



Consider what happens when a gas is heated. The 

 heat that is communicated to it may take any or all of 

 the following forms : — 



A. Kinetic energy of translation of the molecules as 



wholes. 



B. Potential energy due to separation of the molecules. 



C. Kinetic energy of the motion of the atoms re- 



latively to the centre of mass of the molecule. 



D. Energy of rotation or vibration of the separate 



atoms regarded as elastic bodies. 



E. Potential energy due to the separation of the atoms 



in the molecule. 



Perhaps a sixth class should be added containing other 

 forms of energy (electrical, etc.), arising from the relations 

 between the molecules and the ether. About this class 

 little or nothing is known, and whether any serious modi- 

 fication in what is said below would result from taking 

 account of it must remain for the future to decide. 



We know that A always takes a share of the heat 

 communicated to the gas. Different molecules will in 

 general have different velocities, and consequently different 



