4H POPULAR LECTURES AND ADDRESSES. 



sidering; or considerably greater than this, to allow 

 for effect of resisting medium. They will fall to- 

 gether for two hundred and fifty years, and though 

 not meeting precisely in the centre as in the first 

 supposed case of no primitive motion, they will, 

 two hundred and fifty years from the beginning, 

 be so crowded together that there will be myriads 

 of collisions, and almost every one of the twenty- 

 nine million globes will be melted and driven into 

 vapour by the heat of these collisions. The vapour 

 or gas thus generated will fly outwards, and after 

 several hundreds or thousands of years of outward 

 and inward oscillatory motion, may settle into an 

 oblate rotating nebula extending its equatorial 

 radius far beyond the orbit of Neptune, and with 

 moment of momentum equal to or exceeding the 

 moment of momentum of the solar system. This 

 is just the beginning postulated by Laplace for his 

 nebular theory of the evolution of the solar system ; 

 which, founded on the natural history of the stellar 

 universe, as observed by the elder Herschel, and 

 completed in details by the profound dynamical 

 judgment and imaginative genius of Laplace, seems 



