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AMERICAN JOURNAL OF SCIENCE 



[FIFTH SERIES.] 



Aet. XXXYII. — A Critical Review of Chamberlin's 

 Groundwork for the Study of Megadiastrophism; by 

 William F. Joxes. 



Summary of Thesis. 



The evidence of earth rigidity and elasticity is here 

 considered from the relative viewpoint and the conclusion 

 is reached that while the earth may be highly rigid under 

 tidal stress, that it is, beneath a superficial shell, in a 

 yield state for stresses of diastrophic dimensions. 



The evidence of seismic transmission apparently indi- 

 cates a viscous liqnid state for depths below 0.6 of the 

 earth's radius for stresses of these dimensions, and the 

 conclusion is reached that such a state for larger stresses 

 will be nearer the surface. 



Seismic transmission indicates an isotropically homo- 

 geneous state for the earth beneath a comparatively thin 

 heterogeneous outer shell and this conclusion is in direct 

 opposition to Chamberlin's postulated earth heteroge- 

 neity both in depth and laterally, and the evidence is taken 

 as indicating a density stratification of the earth as a 

 result of its having passed throngh a period of fusion. 



The postulate of a continuously solid state for the 

 earth is shown to rest on certain assumptions as to size 

 of the earth nucleus and its rate of growth, and a solid 

 heterogeneous earth with vulcanism a result of selective 

 liquefaction is thought to be incompatible with the facts 

 of occurrence of the igneous rocks. 



Evidence is submitted to show that diastrophism can 

 be readily accounted for by adjustment or lack of adjust- 

 ment of a heterogeneous outer shell resting on an asthen- 

 osphere or yield zone, and does not require deep-seated 

 variations of density or deep-seated diastrophic move- 

 ments. 



Am. Jour. Sci.— Fifth Series, Vol. Ill, No. 18.— June, 1922. 



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