PHILOSOPHICAL TRANSACTIONS. 
I. The Kinetic Theory of Planetary Atmospheres. 
By G. H. Bryan, Sc.D., F.B.S. 
Keceived March 15,—Read April 5, 1900. 
1. The possibility of applying tlie Kinetic Theory to account for the presence 
or absence of different gases in the atmospheres surrounding the various members of 
our Solar System, and in particular to explain the absence of any visible atmosphere 
from the Aloon, was first discussed by AYaterston in 1846, in his memoralfie paper 
on “ The Physics of Media,” that so long remained unpidffished in the archives of 
the Boyal Society.* This application of the theory is distinctly mentioned in tlie 
abstract of Waterston’s paper published in 1846,t which is reproduced by Lord 
IIayleigh as an appendix to the paper itself Hence we may say that the kinetic 
theory of planetary atmospheres is as old as the kinetic theory of gases. 
The present subject received the attention ot Dr. Johnstone Stoney somevdiere 
about the year 1867. It was brought under my notice by a note written by Sir 
Robert Ball in 1893,| and in that year I read a pa})er before the Nottingham 
meeting of the British Association on “ The Moon’s Atmosphere and tlie Kinetic 
Theory,” in which numerical results were obtained sufficing to account for the 
absence of a visible atmosjDhere on the Moon and the existence of such gases as 
hydrogen in presence of the Sun. At that time, ho^vever, 1 did not see clearly liow 
to take account of axial rotation, which evidently might play an important part in 
whirling ofi* the atmospheres from certain planets, and thus the results given only 
represented the state of affairs at points along the polar axes of the bodies in (juestion. 
Owing to this objection I did not deem it desirable to publish a more detailed pajier 
than the abstract which appeared in the Nottingham lieport.§ 
In the following year I published a note “ On the Law of Molecular Distribution in 
the Atmosphere of a Rotating Planet,” as an appendix to my Report on the Kinetic 
* ‘Phil. Trans.,’ A, 1892. 
T ‘ Proc. Roy. Soc.,’ vol. 5, 2 ^. 604. 
I ‘Science,’ February 24, 189.3. 
§ ‘ British Association, Nottingham Re 2 Jort, 1893, 2 ^. 682. 
VOL. CXCVL—A 274. B 
18.2.1901 
