SYMPOSIUM OX RADIOACTR-ITY. 69 



to have been for the time being under the local conditions of 

 pressure, state of strain, nature of material, means of escape, and 

 other properties that affected liquefaction and extrusion. It waj 

 regarded as essentially a cune of equilibrium betn-ceri solidity 

 and liquefaction accommodated to the conditions present at each 

 depth and at each stage and was tnaintaitied automatically. The 

 actual cune as thus assigned continued akvays to be essentially 

 the liquefaction curve after that zvas once attained.^^ The view 

 excludes automatically all internal temperatures higher than the 

 local liquefaction temperatures and of course excludes all perva- 

 sive gaseous conditions except that of the interspersed and 

 occluded gases of the mixed mass. These interspersed gase% 

 assisted extrusion and hence were among the parts most freely 

 extruded. All theoretical inferences based on temperatures 

 higher than the temperatures of liquefaction are excluded from 

 consideration under this view by its very terms. 



Certain structural conditions postulated by the planetesimal 

 hypothesis greatly favored this automatic action. The infaUing 

 matter was assumed to have built itself up in a very heterogeneous 

 manner with the result that the mass of the earth was an intimate 

 mixture of all the kinds of material that made up the spiral nebula 

 from which it was supposed to have been gathered. As this mixed 

 matter was heated by compression, some parts of it must certainly 

 have reached temperatures at which they could go into mutual 

 solution or into fusion while as yet other closely associated part«; 

 had not reached temperatures that permitted such action, and as 

 the rise of temperature was verj- slow by the terms of the hypoth- 

 esis the passage of successive parts into liquefaction was widely 

 separated in time. Fluid parts thus came temporarily to be inti- 

 mately mixed with solid parts. These fluid parts, in the act of 

 passing into solution or fusion absorbed the necessar}- energ\- of 

 liquefaction at the expense of the increasing supply. On their 

 ascent into the crust they heated it. If they lodged there and 

 resolidified they gave up their heat of liquefaction. If they 

 reached the surface the residue of heat, both sensible and latent, 

 was lost. By such liquefaction and transfer these portions served 

 to protect the residue in the deeper parts from liquefaction for 

 the time being and the continuation of the process extended the 

 protection to such residue as continued to persist. 



It is not necessary to otter evidence that ascent of liquid rock 



"Loc. eit., p. 567. 



