36 FROM NEBULA TO NEBULA 



ference, however, that whereas the planet necessarily 

 revolves as a solid piece, every individual particle of the 

 nebula revolves in a free orbit round the common center 

 of gravity of the joint mass. 



To cite a historical incident by w r ay of helpful illus- 

 tration: Until the year 1857, the rings of Saturn were 

 supposed to be solid, but in that year James Clerk Max- 

 well wrote an essay, "On the Stability of Motion of 

 Saturn's Rings" (winning thereby the Adams prize at 

 Cambridge), in which he argued the thesis that they 

 could not be stable if solid or liquid, and hence must con- 

 sist of discrete particles. This conclusion was later con- 

 firmed by Professor J. E. Keeler by means of the spec- 

 troscope. 



3. In my criticism of the Laplacian conception, it 

 will be remembered, I pointed out how he sought to 

 explain the remarkable coincidences and harmonies 

 characterizing our system by the wholesale postulate 

 that the nebula rotated of itself as one piece. I recognize 

 as did he the necessity of this concert of movement, but 

 instead of postulating the uncertain and impossible self- 

 existence of motion, I seek the explanation in a dynami- 

 cal factor sufficiently powerful and comprehensive, not 

 only to account for the starting of the gyrations, but to 

 ensure automatically their manifold mutual adjustments 

 and their continuance. Incidentally let me impress upon 

 the reader that in postulating inherent motion Laplace 

 was obliged to assume primordiality for his nebula, 

 thereby implying an actual Beginning to the cosmos and 

 definitely committing himself to the teaching that all 

 nebulae which show signs of rotation are necessarily 

 primal. I, on the contrary, regard all nebulae as inter- 

 mediate forms between other states of existence, and 

 amenable to natural laws without special privileges or 

 immunities. 



Let us return again to the contemplation of the 

 nebula, which we assumed as being produced by a solar 

 explosion. It could, perhaps, be fairly pictured as 

 initially spherical in outline, but more probably it would 



