VOLUME XXVIII NUMBER 6 



THE 



JOURNAL OF GEOLOGY 



SEPTEMBER-OCTOBER iq2o 



DIASTROPHISM AND THE FORMATIVE PROCESSES 



XII. THE PHYSICAL PHASES OF THE PLANETARY NUCLEI 

 DURING THEIR FORMATIVE STAGES 



T. C. CHAMBERLIN 

 The University of Chicago 



In an article in the first number of this volume of the Journal 

 a study of the relative densities of the moon, Mars, Venus, and the 

 earth brought out the fact that the mean densities of these bodies 

 not only rise in the order of their masses, but that the rate of increase 

 itself rises with each unit-increase of mass."" This led to a study of 

 the processes by which these bodies acquired their material, to see 

 whether any part of the observed higher density could reasonably 

 be assigned to greater proportions of inherently heavy material 

 received during their formation. The conclusion was reached that 

 larger proportions of light material entered into the formation of the 

 large bodies than into the small bodies. The natural inference 

 from this is that the higher mean densities now found in the larger 

 bodies are due to some form of mass-effect that was sufficient to 



* "The Order of Magnitude of the Shrinkage of the Earth deduced from Mars, 

 Venus, and the Moon," Jour. Geol., Vol. XXVIII (1920), pp. 1-17. Compare 

 this with the theoretical deductions of Dr. A. C. Limn, " Geophysical Theory under the 

 Planetesimal H>'pothesis, in the Tidal and Other Problems," Carnegie Institution 

 Publication No. loj (1909), particularly pp. 188 and 201. Compare also the very 

 suggestive paper of Dr. Wm. D. MacMillan "On Stellar Evolution," Astrophys. 

 Jour., Vol. XLVIII (July, 1918), pp. 36-40. 



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