132 JAMES CLERK MAXWELL 



ft = 1*634.. Now, Maxwell's theory required that for 

 smooth hard particles, approximately spherical in 

 shape, ft should be 2, and hence ho concludes " wo 

 have shown that a system of such particles could not 

 possibly satisfy the known relation between the two 

 specific heats of all gases." 



Since this statement was made many more experi- 

 ments on the value of 7 have been undertaken ; it is 

 not equal to 1-408 for all gases. Hence the value of 

 ft is different for various gases. 



It is of some importance to notice that tho 

 value of ft just found for air is very approximately 

 1-GG or J. 



For mercury vapour tho value of 7 has been shown 

 by Kundt to be 1*33 or 1 J, and hence ft is equal to I. 

 Thus all the energy of a particle of mercury vapour Ls 

 translational, and its behaviour in this respect is con- 

 sistent with the assumption that a particle of mercury 

 vapour is a smooth sphere. 



Tho two results of this theory which seemed to 

 lend themselves most readily to experimental verifi- 

 cation were (1) that tho viscosity of a gas is 

 independent of its density, and (2) that it is pro- 

 portional to tho square root of the absolute 

 temperature. The next piece of work connected with 

 the theory was an attempt to test these consequences, 

 and a description of the experiments was published 

 in the "Philosophical Transactions" for 18(35, in a 

 paper on the " Viscosity or Internal Friction of Air 

 and other Gases," and forms the Bakcrian lecturo lor 

 that year. 



The first result was completely proved. It LH 



