MONATOMIC GAS: DIFFUSION, VISCOSITY, AND THERMAL CONDUCTION. 197 
Note E. (To pp. 158, 184, 185.) 
[In a note recently communicated to the ‘ Philosophical Magazine/ I have considered thermal diffusion 
in the case of two molecules nearly or quite equal in mass, and very unequal in size. If the difference of 
mass is sufficiently small, the larger molecules will tend towards the cooler regions .—April 30, 1917.] 
Note F. (To p. 115.) 
[In his ‘Inaugural Dissertation,’ Upsala, 1917 (received just before the final revision of the proofs of 
this paper), D. Enskog gives a mathematical theory of simple and composite monatomic gases, based upon 
Boltzmann’s integral equation for the velocity-distribution function. The method of solution is, however, 
different from that of his 1912 paper. The numerical and other results, including those relating to 
thermal diffusion, are in agreement with those of this paper, though not always identical in form. While 
perhaps less developed from the physical standpoint, Dr. Enskog’s work is mathematically much the more 
complete. His elegant and accurate proofs will materially lighten the task of proving my own work to 
be in conformity with Boltzmann’s equation .—April 30, 1917.] 
