THE AUTHOR'S THEORIES OUTLINED 63 



9. In the matures! stars the shell is so well diffused 

 and fluid throughout that ebullition within it can go 

 on freely, and consequently they experience no inter- 

 mediate extraordinary eruptions, which are the only 

 sort, of course, that can explain variability. In the 

 second grade of stars, again, the shell is also very fluid, 

 but not clear through, as in the first grade, so that there 

 is a tendency to clog in the lowest strata, but only at very 

 great intervals, while ebullition in the superincumbent 

 layers proceeds freely. At the other end of the scale, 

 on the other hand, we find the shell possessing a compara- 

 tively shallow fluid covering in which the distinctive 

 variation-producing eruptions accordingly take place at 

 only a slight depth, and, consequently, with greater fre- 

 quency. As general conclusions, then, we may state, (1) 

 that the variability of stars is functioned on their mass, 

 (2) that the maturest stars have no distinct variation 

 save that of final disruption into 'nebulae, and (3) that 

 the smaller the star the shorter and more uniform its 

 period of display. 



THE GENESIS OF THE SOLAR SYSTEM 



Nature, like man, often has a variety of ways for ac- 

 complishing a given result. Thus she may level the tree 

 with the sword of her lightning, the breath of her storm 

 or by decay, or the woodman may fell it with the blows 

 of his axe or the blast of dynamite. That the Great 

 Pyramids were built by human hands we well know, yet 

 we count it no disgrace that our historians and engineers 

 alike have failed to discover their architectural secret. 

 So in our efforts to fathom the precise genesis of the 

 solar system many details will doubtless have to remain 

 unresolved, even though we may be able to define the 

 methods which lay open to Nature's choice. 



1. We may imagine, to begin with, a great nonde- 

 script cloud of primordial cosmic dust suddenly being 

 galvanized into action by the divine edict, Fiat Gravitas, 

 and then crystallizing into nuclei here and there; some, 



