for the Study of Megadiastrophism. ±05 



then to, on this basis, deduce a great compression reduces 

 the conclusion to an assumption. The reverse line of 

 reasoning was adopted when the determinations of earth 

 rigidity for seismic and tidal stress were taken to indicate 

 a similar rigidity under diastrophic stress conditions. 



An earth coarsely stratified by density due to composi- 

 tion rather than compression more readily conforms to 

 the earth's seismic and magnetic properties and can also 

 meet any requirements of rigidity placed upon it. Such 

 an arrangement implies a stage of fusion. 



The Molten Stage. 



Rate of Growth of the Earth. — If the fundamental 

 postulates of the planetesimal hypothesis be accepted then 

 the question as to whether or not the earth passed through 

 a molten stage at its present size rests upon the assumed 

 size of the original earth nucleus and its rate of growth. 

 Now any conclusion as to the size of this nucleus is pure 

 assumption, but whatever its size at any rate, it passed 

 through a stage of fusion. In order then to secure and 

 maintain solidity through the period of growth only one 

 set of assumptions can be adopted and there are, first, a 

 nucleus of relatively small mass and, second, an exceed- 

 ingly slow rate of growth. These constitute the basic 

 foundations of the groundwork for the study of megadi- 

 astrophism. 



The question of fusion is a question of heat generation 

 per unit time, or temperature. It hinges then not so 

 much on the size of the nucleus but on the rate of growth, 

 for this would largely determine the temperatures 

 attained. Kate of growth in turn depends largely upon 

 the orbital dynamics of the interplanetary dispersed 

 material and the ability of the earth nucleus to gather 

 it in. 



Chamberlin pictures as the task set for the nucleus, 

 which he assumes to have a diameter of 6,000 miles, the 

 clearing up of a belt 55 by 58 by 592 million miles. 29 

 Gravitation is ignored and growth is assumed to be due 

 entirely to orbital conjunction. Can gravity be so 

 ignored 1 



29 Op. eit. 3 p. 409, 410. 



