258 T. C. Chamberlin — Jones's Criticism of 



improved by listing reserved and cautious students of the 

 doctrine as its fundamental and necessary opponents. 



Where then does the sharp issue really lief — During the 

 last century and before, a molten earth was almost uni- 

 versally accepted by geologists. It was a logical infer- 

 ence from a self-developing or monoecious planetary 

 evolution, whatever its particular form. During the first 

 decade of the present century, an origin by means of a 

 dioecious, or cooperative, or bi-parental evolution was 

 proposed, because the conviction had been reached that no 

 monoecious system of evolution could give rise to the 

 singular dynamic features presented by our planetary 

 system. This postulated cooperative evolution was such 

 as to give rise to a growth of the earth essentially in a 

 solid state by means of the slow ingathering of planetesi- 

 mals. There thus arose a radical difference between two 

 classes of postulates because of their cosmological inheri- 

 tances. The practical difference between them centered 

 in a molten vs. a solid state of the earth. Along these 

 lines, there is a fundamental issue. 



As a sub-phase in the development of the accretional 

 view, an attempt has been made to cut off the top of the 

 standard planetesimal tree, so to speak, and graft on the 

 stump a molten state instead. I have not specifically dis- 

 cussed, in print, the congeniality of such engrafting, and 

 I am reluctant to do so now — for personal reasons too 

 obvious to need mention — but it is made necessary. 



7s a molten state compatible with a planetesimal origin® 

 — The planetesimal basis is herein taken for granted. If 

 the conditions of formation thus postulated permitted 

 free speculation, it might be assumed that the planetesi- 

 mals were gathered in fast enough to force a molten state. 

 But the postulated conditions are far from permitting 

 free speculation ; they are rather severely restrictive as 

 we shall at once see. 



A molten state under planetesimal conditions could 

 normally arise only when the mass of the nucleus was 

 large enough to give great heat by its own condensation 

 and, at the same time, had strong enough attraction to 

 draw in the planetesimals rapidly, and even then the 

 planetesimal orbits must be favorably distributed. There 

 is no gain by supposing that the planetesimals grew into 

 large masses, for (1) there would be some loss of energy 



