DIASTROPHISM AND THE FORMATIVE PROCESSES 487 



would seem to invite a more direct and simple convection, but they 

 might be specially subject to influence from the inherited motions. 

 For example, if the rotation were west-east, like the sun's rotation 

 in which the mass participated before ejection, and there were a 

 north-south axial movement as in the case of the eruptions of May 29 

 and July 15, 1919, cited above, there might naturally be inherited 

 from this an axial movement from one pole through the center 

 to the other. The original tenuous state would apparently be favor- 

 able to this, and, once established, it might be perpetuated as an 

 effective form of central convection. A special interest attaches 

 to this from its possible influence on the solid core as that gradually 

 formed — but this cannot be discussed here. 



The point to be emphasized is the inevitable subordination — 

 in the early formative stages — of the convection actuated by differ- 

 ence of temperature to the inherited motions. The circulation, far 

 from being simple descent and ascent, was tortuous and involved, 

 and the core-forming process must be interpreted on this basis. 



II. The molecular sifting of the nuclei required to reduce the 

 original solar gases to the composition of the present solid bodies. — ■ 

 The nuclei of the giant planets may be passed by, merely remark- 

 ing that there is little reason to think they suffered much sifting; 

 rather they seem to have been so massive from the outset that they 

 retained all classes of molecules that came under their control. 

 By far the larger number of the solid bodies of the solar system, 

 however, are practically devoid of free gases, and seem to be 

 formed almost wholly of stony and metallic matter. None of the 

 terrestrial planets carry more than a very small percentage of free 

 gases; apparently almost their whole substance consists of stony 

 and metallic materials such as make up the main body of the earth 

 and of meteorites. 



The original gases of all the bodies derived from the sun, large 

 and small alike, should have had essentially the same composition. 

 Spectroscopic analysis shows that the visible substance of the sun 

 is an intimate mixture of many kinds of molecules. Unfortu- 

 nately, their relative proportions can merely be inferred in a general 

 way. The low density of the sun (1.40), notwithstanding its 

 great mass, implies — even when its high temperature is considered — • 



