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CARNEGIE INSTITUTION OF WASHINGTON. 



trol. The subsequent assemblage would not then be that of a gas, but 

 would apparently proceed by a process quasi-gaseous in part and quasi- 

 orbital in part. A reduction of the collision-rebound type of action 

 would apparently follow with a relative increase of orbital motion. 

 Computation based on the data given in table 3 seemed to show that 

 all the atmosphereless bodies of the solar system, and probably those 

 that have small atmospheres, were formed along this line of descent 

 which may be looked upon as an alien derivative from the true gaseous 

 line of descent. 



Table 3. — Dynamical properties of ten representative bodies of the terrestrial and smaller 



classes* 



♦Computations by W. D. MacMillan. 



It is not altogether clear which of these two lines of descent was 

 followed by the nucleus of the earth, for the size of this nucleus relative 

 to the adult mass of the earth depends upon considerations which it 

 seems best not to try to evaluate until the inquiry is more advanced. 

 If the concentration of the earth nucleus followed the derivative line 

 just sketched, the core of the earth was probably solid at all stages and 

 the whole of the bodily evolution essentially accretionary, but if it 

 followed the gaseous-Brownian-mixture line, the method of solidifi- 

 cation of a hquid core under such peculiar conditions needs reconsidera- 

 tion on the lines that actually obtained, as nearly as these can be 

 determined by patient and critical analysis, and not on the supposi- 

 titious lines of ideal isolated gaseous bodies. 



