66 PROCEEDINGS OF SECTION 4A. 
trolling sun, so immensely greater than that of the attendant 
planets, is, so far as our actual knowledge is concerned, 
unique in type. But we are becoming acquainted with an 
increasing number of systems (the double stars), in which we 
have two bodies revolving round one another, always com- 
parable, and frequently enough nearly equal im mass. Dr. 
See has called our attention to the important part which 
tidal friction must play in the life-history of such systems, 
the evolution of which must be on an entirely different pian 
to that of our own. Investigating im a very thorough way _ 
the orbits of 40 known bimaries, Dr. See finds that the 
average eccentricity of their orbits is 12 times as great as the 
average eccentricity found in the orbits of the planets. If 
we can imagine two bodies, each as big as our sun, revolving 
round one another, each in a hot plastic condition, it is clear 
that the tidal effects produced must be enormous; and one 
of the results of tidal friction is that the eccentricity of the 
orbit is continually increased. So, that the high eccentricity 
of all these double-star orbits forms corroborative evidence 
of the truth of the theory. “In many of the spectroscopic 
binaries the two stars appear to be revolving exceedingly 
close together, if not in actual contact, and as our knowledge 
of these double stars becomes greater, we may possibly be 
able to see presented to us in the heavens the whole of the 
different stages in the past life-history of the earth and 
moon. 
It may appear to many that such speculations are un- 
profitable, in that they are incapable of verification. You 
all probably remember Herschel’s oft-quoted analogy, in 
which he compares our position to that of a travelier in a 
forest. | The traveller is not able actually to see the growth 
of the trees around him, but yet he may, by an examination 
of the trees in the different stages of youth and age, arrive 
at a very accurate notion of the way in which the tree 
grows. We are far at present from actually realising this 
conception ; but, if we can, by a similar process of ‘reasoning, 
arrive at a knowledge of the way in which m our earth and 
its companion moon have reached the present stage in their 
history, we shall surely have done something which may well 
be regarded as a magnificent triumph of human intelligence. 
