224 PROGRESS OF SCIENCE IN THE CENTURY. 



solar system has been to discredit the details of La- 

 place's hypothesis in a variety of ways, hut to estab- 

 lish on a firmer basis the general view that the solar 

 system has been formed by some process of condensa- 

 tion out of an earlier very diffused mass bearing a 

 general resemblance to one of the nebulce which the 

 telescope shows us, and that stars other than the sun 

 are not unlikely to have been formed in a somewhat 

 similar luay ; and, further, the theory of tidal friction 

 supplements this general but vague theory, by giving 

 a rational account of a process which seems to have 

 been the predominant factor in the development of 

 the system formed by our own earth and moon, and 

 to have had at any rate an important influence in a 

 number of other cases/' 



