for the Study of Megadiastrophism, 



403 



tion on any other assumption than that the earth is, in 

 a large sense, a yielding body. 



Density Arrangement Within the Earth. — It is evident 

 that the material within the earth is more dense than 

 the visible material and it is also evident that the density 

 becomes greater with depth though whether this increase 

 continues" to the earth's center is problematical. If now 

 the earth is heterogeneous in its constitution from the 

 surface downward then increase in density would be 

 due to increasing pressure and the consequent condensa- 

 tion. This state, as postulated by Chamberlin, implies 

 a chemical constitution throughout the earth, in general, 

 similar to the visible terranes. TVhile he has admitted 

 the possibility of the accumulation of more dense material 

 near the center through the process of selective liquefac- 

 tion 22 Chamberlin's final conclusion is that "the metallic 

 theory fits only clumsily the growing evidence that the 

 interior elasticity and rigidity rise faster than density," 23 

 and again, "the tenor of accumulating evidence implies 

 that the conditions which affected the progressive self- 

 compression of the body were more important than those 

 which affected the original assortment of the material." 24 

 The one-fifteenth volume "core" is given finally a density 

 stratification since it was concentrated, by hypothesis, 

 through a "gaseo-niolten" line of descent and would 

 "take on a more or less concentric structure similar to 

 that logically assigned to the whole earth by the old- 

 masters." 25 The final picture is then of a central core, 

 one-fifteenth of the earth's volume, stratified by density; 

 surrounded by a shell composed of crystalline hetero- 

 geneous material, the density of the whole mass being 

 due to self-compression. 



The large percentage of metallic alloy in meteorites, 

 even taking into consideration the large number of stony 

 meteorites which are unnoticed, would imply a similarly 

 large percentage of metal in the earth, and if present, 

 and not concentrated towards the center, the surficial 

 earth material should contain more of it and have a 



22 T. C. Chamberlin: Origin of the Earth, Chicago, 1916, p. 1S1 and 

 p. 237. 



23 T. C. Chamberlin: The Greater Earth, Bull. Geol. Soc. Am., vol. 32, 

 p. 224, 1921. 



24 Ibid., p. 223. 

 23 Ibid., p. 221. 



