DIASTROPHISM AND THE FORMATIVE PROCESSES 155 



It scarcely need be added that the severest selection of heavy 

 molecules would be realized in the smallest knots where the struggle 

 to maintain themselves was most strenuous, and that in the inter- 

 mediate class the percentage of heavy molecules would be inversely 

 proportional to mass. 



All this relates to the purely molecular state assumed to prevail 

 while the knots were organizing themselves out of solar ejections 

 and were beginning their careers as the nuclei of growth into mature 

 planets, planetoids and satelKtes. 



3. Let us turn now to the inner evolution of these nuclei. Let 

 us recall that immediately on the emergence of the gas-masses 

 from the sun there was great expansion and much cooling in con- 

 sequence. Rapid radiation must have followed as the expanded 

 mass shot out into the relatively cold space of the outer regions. It 

 seems inevitable therefore that the condensation temperatures of 

 the refractory material that now makes up most of the sohd body 

 of the earth, and doubtless of its neighbors, would be reached at a 

 succession of stages relatively early in the history of the medium 

 and smaller order of knots. We may assume that the condensation 

 into minute spherules was started by electric charges and followed 

 essentially the Hnes already sketched in the study of the derivatives 

 from a rotating spheroidal nebula. There was this difference, 

 however. The centrifugal derivatives from the rotating nebula 

 were planetesimals each following its own orbit. The condensa- 

 tions within the nuclei were, at first at least, scattered through the 

 uncondensed portion that was still gaseous. The condensed 

 spherules or crystals were like cloud particles or dust particles in an 

 atmosphere. Dynamically they were like Brownian particles, 

 jostled about by the impacts of the molecules that still remained in 

 the gaseous state. They would naturally develop earhest in the 

 outer parts of the nuclei and later in the inner parts. They would 

 constitute a class of bodies heavier than the molecules and would 

 tend to damp molecular action, while they themselves would tend 

 to faU toward the center of the nuclei, but their fall would be re- 

 sisted by the part that remained gaseous. It is obvious that the 

 condensation of the refractory heavy material into spherules or 



