VOLUME XXVIII Number 8 



THE 



JOURNAL OF GEOLOGY 



NOVEMBER-DECEMBER 1920 



DIASTROPHISM AND THE FORMATIVE PROCESSES 



XIII. THE BEARINGS OF THE SIZE AND RATE OF INFALL 



OF PLANETESIMALS ON THE MOLTEN OR SOLID 



STATE OF THE EARTH 



T. C. CHAMBERLIN 



University of Chicago 



In the last article of this series^ it was found (i) that the solar 

 gases, as they were expelled to form the planetary systems, were 

 so mixed that they were unfitted to form solid bodies such as the 

 terrestrial planets, the planetoids, and the satellites, until after 

 they had been sifted by a selective process, (2) that the sifting 

 process introduced such a serious departure from familiar modes of 

 gaseous condensation as to require reinterpretation, (3) that the 

 process of concentration was also complicated by inherited motions, 

 (4) that it was still further conditioned by the formation of pre- 

 cipitates and precipitate aggregates, and (5) that the planetary 

 cores, while in process of formation, were subjected to viselike 

 squeezing, more intense below than above, followed by partial 

 relaxation, so that selective extrusion attended the closing pro- 

 cesses, involving the ascent of the lighter mobile matter and the 

 compression and reorganization of the rest, thus contributing 



' " Diastrophism and the Formative Processes. XII. The Physical States of 

 the Planetary Nuclei during Their Formative Stages," Jour. Geol., Vol. XXVIII 

 (1920), pp. 473-504- 



66s 



