﻿316 W1L0OCKS' REFLECTIONS ON THE 



Having now obtained a foundation based upon astronomical necessity, let us ask, 

 has there ever been conceived an hypothesis designed to account for cosmical phe- 

 nomena more important, and more thoroughly explored, than those pertaining to this 

 star, and which, when applied to the latter, may yield an explanation ? 



We answer, yes. The Nebular Hypothesis of La Place was designed for such a 

 purpose, and having for half a century stood the fire of the world's criticism, has 

 passed that ordeal unscathed, and now holds an almost undisputed empire upon the 

 minds of astronomers. 



Meditating upon the relations which the different bodies of the solar system bear 

 to each other, with the view of arriving at the probable cause of the same, La Place 

 directed his attention to the following phenomena.* 



1st. The uniformity in the direction of the orbital motion of the planets, and the 

 near coincidence of their planes. 



2d. The conformity in the direction of the axial rotation of the sun and planets, to 

 the orbital motion of the latter, and the slight difference of the planes. 



3d. The small eccentricity, of the orbits of the planets and their satellites. 



Finally the great eccentricity of the orbits of the comets. 



La Place was influenced in his reflections by the telescopic appearance of certain 

 stars noticed by Sir Win. Herschel, which seemed to be in various stages of progress 

 towards completeness. 



The views which he was led to adopt, after severe study, were the following : 



1st. The primordial condition of the sun was that of a nebula of extreme tenuity, 

 having a revolution upon its axis. 



2d. By the gravitation of the particles of the nebula, a condensation occurred 

 at its centre. 



3d. At this period the sun was in the condition of those telescopic stars which are 

 observed to consist in a nucleus, surrounded by a nebulous haze. 



4th. The contraction of the matter caused such an increase of the angular velocity 

 at the surface of the nebula, that, by the centrifugal force, the particles about the 

 equator were separated from the mass, and left in the form of a ring. 



5th. The formation of rings occurred at successive epochs, and eventually became 

 planets. 



6th. It was within the range of possibility that a ring should continue unbroken, 

 or that it should separate into many fragments. The solar system furnishes examples 

 of each of these extremes. 



The views which we shall offer require the mean of the extremes proposed by 

 La Place, viz. : that of a ring with a single solution of continuity. 



Systeine du Monde, p. 409. 



