200 T. C. CHAMBERLIN GROUNDWORK OF EARTH S DIASTROPHISM 



long as the gaseous condition remained. While in this active fluid state 

 the possibilities of chemical combination of the earth substances should 

 have exhausted themselves so far as temperature permitted. So, also, 

 should the physical adjustments of the matter. According to the old 

 masters, whose logic was admirable, the heaviest substances should have 

 gathered at the center, the less heavy next, and so on in order, the lightest 

 forming the outer layer. Thus the earth should have taken on almost 

 perfect symmetry, and at the close of the assembling process it should 

 have been in perfect isostatic equilibrium, both vertically and horizon- 

 tally. 



Thus we see that, to a maximum degree, the potential energies repre- 

 sented in the original deployed state should have been converted into 

 fugitive forms of energy and have been dispersed before any diastrophic 

 record could he made. There was little possibility of shrinkage left ex- 

 cept the meager amount that could arise from further cooling. 



The conservative Type 



On the other hand, if we neglect for the time being so much of the 

 central part of the earth as is supposed to have been formed from the 

 earth nucleus, as defined in the preceding article, and assume that the 

 outer and much larger part was built up of planetesimals or planetesimal 

 dust, in a relatively cool and solid state, an earth of very different poten- 

 tial resources of diastrophism would arise. To fully realize this, it should 

 be noted that after the earth had reached the mass of Mars it should 

 have been able to hold a notable atmosphere. All the planetesimals that 

 made up the later growth must have plunged through this atmosphere 

 after the fashion of meteorites on their way to the earth. Their veloci- 

 ties Avere thereby checked and their substance more or less converted into 

 dust.^ 



The outer mass of the earth, built up thus at random by the infall of 

 mixed clastic material, should have been highly porous and should have 

 retained almost a maximum of susceptibility of compression in a solid 

 state. Moreover, the distribution of the infalling matter by the atmos- 

 phere and hydrosphere should have been irregular, so that compression 

 must have worked on uneven textures as well as var3dng substances, and 

 lience should have produced distortion. As this was the distortion of 

 solid matter, it should have retained a record of the action. 



The mass as first built up should have been heterogeneous in chemical 

 composition and almost totally devoid of adjustment in respect to density 



- For a discussion of the size, rate of infall. and physical condition of planetesimals. 

 see Article xiii. Diastrophism and the formative processes. Jour, of Geol.. vol. xxviii. 

 (1920), pp. 665-701. 



