THE EVOLUTIOJ^ OF SATELLITES.^ 



By G. H. Dakwin. 



I. 



The Atlantic Monthly for October, 1897, contains an interesting- 

 paper by Mr. See on "Eecent discoveries respecting the origin of the 

 universe." In the present article I propose to explain, in greater 

 detail than the necessary limitations of space permitted him, the 

 theory which forms the point of departure for his speculations. 

 Although the natural sequence is thus inverted, it may be hoped that 

 the postponement of explanation to application will be condoned. In 

 any case, this article owes its origin to the former one, and it might not 

 otherwise have been justifiable to expound a theory which was laid 

 before the scientific world some fifteen years ago in the pages of the 

 Philosophical Transactions of the Eoyal Society.^ 



After the explanation of this theory I have added some comments on 

 Mr. See's views. 



II. 



If familiarity does not always breed contempt, yet at least it gener- 

 ally breeds indifference. This is the case with most of us in regard to 

 the rise and fall of the tide by the seashore, and so the problem as to 

 whether the tide will serve conveniently to allow the children to dig 

 in the sand or search for seaweed looms larger than that presented by 

 the gigantic forces which now produce only these somewhat insignifi- 

 cant pulsations of the sea. Yet the tides should call forth in us a 

 deeper interest — I might almost say an emotion — for, as I shall show, 



' Eeprinted. from the Atlantic Monthly of April, 1898, by permission of the pub- 

 lishers. This article forms a portion of Mr. Darwin's forthcoming work On Tides. 



2 It was very natural that Mr. See should find in certain tidal investigations which 

 I undertook for Lord Kelvin the source of my papers, but as a fiict the subject was 

 brought before me in a somewhat different manner. Some unpublished experiments 

 on the viscosity of pitch induced me to extend Lord Kelvin's beautiful investigation 

 of the strain of an elastic sphere to the tidal distortion of a viscous planet. This 

 naturally led to the consideration of the tides of an ocean lying on such a planet, 

 which forms the subject of certain paragraphs now incorporated in Thomson and 

 Tait's Natural Philosophy. 



lOB 



