62 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. [DeC. 17, 



same conclusions would hold true almost in the same degree, if the 

 time since the glacial period, or the velocity with which the sun is 

 moving, be much greater than above supposed. I think it clear, 

 therefore, that the cold of the glacial epoch cannot be attributed to 

 the cause we are now discussing. 



8. As far as we are acquainted with the disposition of the stars 

 not very remote from our own position in stellar space, it would seem 

 probable that the distances of the stars from each other are such that 

 there are no points at present among them at which the intensity of 

 radiating heat is comparable to that which the earth derives from the 

 sun, except at points so near to each star that the heat derived from 

 it is incomparably greater than from any other star. Thus, if the 

 earth could derive a degree of heat from stellar radiation comparable 

 with that now derived from the sun, it could only be by her close 

 proximity to some other particular star, leaving the aggregate effect 

 of radiation from the other stars nearly the same as at present. This 

 approximation of position to a single star, however, could not take 

 place consistently with the preservation not only of the remoter 

 bodies of the solar system, but even of the motion of the earth about 

 the sun, according to its present laws. 



Suppose our sun should approach a star within the present distance 

 of Neptune. That planet would no longer remain a member of the 

 solar system, and the motions of the other planets would be dis- 

 turbed in a degree which no one has ever contemplated as probable 

 since the existence of the solar system. But such a star, supposing 

 it to be no larger than the sun, and to emit the same intensity of 

 heat, would not send to the earth much more than one-thousandth 

 part of the heat which she derives from the sun, and would therefore 

 produce only a very small change of terrestrial temperature. 



The only case I can conceive which might possibly be consistent 

 with the continued existence of the solar system in nearly its present 

 form, and in which stellar radiation might produce any great effect 

 on terrestrial temperature, would be that in which the sun should be 

 surrounded by an immense group of stars, and that their proximity 

 should be sufficient to give effect to their radiation, while their 

 arrangement should produce a mutual counteraction of their dis- 

 turbing influences on the planetary motions. But such a group of 

 stars must be sought for in some portion of the stellar space remote 

 from the region which the solar system now occupies, or in a new 

 grouping of the stars by their own proper motions, in the space 

 immediately surrounding that region ; and such changes, if they be 

 possible or conceivable at all, must necessarily require periods of time 

 which would render the theory utterly inapplicable to the explanation 

 of the changes of temperature at the more recent geological epochs. 



