l6 THOUGHTS ON NATURAL PHILOSOPHY. 



granules of matter must, consequently, have travelled 

 at terrific speed; and moving through points in a 

 circle or circles must when they clashed have pro- 

 duced so high a temperature as to give by their 

 motion the necessary logical and mathematical basis 

 for the nebular hypothesis of Laplace. A short 

 account of this hypothesis is given in the Encyclopedia 

 Britannica as follows : 



The nebular theory is a famous hypothesis which 

 has been advanced with the view of accounting for 

 the origin of the solar system. * It is emphatically 

 a speculation; it cannot be demonstrated by obser- 

 vation or established by mathematical calculation. 

 Yet the boldness and the splendour of the nebular 

 theory have always given it a dignity not usually 

 attached to a doctrine which has so little direct 

 evidence in its favour. It will also be admitted that 

 from the very nature of the case a theory of the 

 origin of the solar system must be devoid of direct 

 testimony. All we could expect to find would be 

 features in that system whose existence the theory 

 would account for; or possibly by looking at other 

 systems we might observe them in phases suggesting 

 the early phases of our own system. It is hard to 

 see what other kind of evidence would be attainable. 

 Now as a matter of fact our system does present 

 many most striking features which could be accounted 

 for by the nebular theory, and the theory also derives 

 as much corroboration from the study of other 

 systems as we could reasonably expect. Hence, as 

 all attainable evidence is on the whole in favour of 



* This was written before the publication of my theory. 



