148 SEE— DYNAMICAL THEORY [April 19. 



It is obvious that masses of such vast extent and perfectly round 

 figure and symmetrical arrangement of internal density, could not 

 possibly have arisen by any of the theories of collision formerly 

 held but now abandoned. For collisions could not disperse the stars 

 to such great distances over spaces measured by many thousands of 

 light years, nor could they give rise to the observed symmetrical 

 arrangement of the parts. IMoreover, clusters embracing thousands 

 of stars, if due to collision, would imply two equally immense masses 

 in collision ; and there would be so few of these large masses in the 

 universe, that it is inconceivable that they would ever come into col- 

 lision. The whole collision doctrine is manifestly inconsistent with 

 the symmetry and order found in the clusters, which can therefore 

 be explained only by the capture theory, based on the expulsion of 

 dust from the stars, and its collection from all directions into masses 

 of impressive symmetry. 



This theory not only gives a perfectly satisfactory account of the 

 phenomena of the clusters, which are wonderful in the extreme, and 

 show steady and uniform processes working slowly over immeasur- 

 able ages; but also establishes the theory itself by the way the most 

 intricate and diverse phenomena are woven into a continuous whole. 



The first rule of philosophy laid down by Newton in the " Prin- 

 cipia " is that: "Wc are to admit no more causes of natural tilings 

 than such as are both trne and sufficient to explain their appearances." 

 He explains this by adding that " philosophers say nature does noth- 

 ing in vain, and more is in vain when less will serve." The next rule 

 is that we are to ascribe the same natural effects to the same causes. 



If therefore the capture theory alone will explain the clusters, 

 where the scale of the operations is immense, and the symmetry so 

 perfect that other causes are easily excluded ; and on the other hand 

 it will equally account for all other known phenomena of the sidereal 

 universe, it follows from Newton's rules for philosophizing that this 

 cause alone can be regarded as established. The definite proof of 

 the capture theory for the formation of clusters and nebulae thus 

 renders its operation general throughout the sidereal universe. 

 Everywhere the large masses drift towards the most powerful neigh- 

 boring center of attraction, while fine dust is expelled from the stars 



