500 T. C. CHAMBERLIN 



factor was not necessarily large relatively, even if the gaseo-molten 

 phase of nuclear history did obtain and is given as generous an 

 estimate as the data will warrant. 



It ought not to be overlooked, however, that the solid core, 

 in its assigned formation by the deposition of crystals or other 

 precipitates from the gyrating currents of the central circulation, 

 would have been very likely to have incorporated inequalities of 

 material and taken on asymmetries of form so as to have pre- 

 sented a deformed foundation, as it were, for the later accretions. 

 Such deformities would have been likely to have made themselves 

 felt in the diastrophism of all that was built upon them. This is 

 a phase of the subject which I hope to pursue further in the future. 



IV. EXTERIOR AGENCIES THAT AFFECTED THE PLANETARY CORES 

 DURING THEIR FORMATION AND AFTERWARD 



The discussion thus far has been confined to agencies acting 

 within the evolving masses. The evolution, however, was not 

 free from influences that acted from without. One type of such 

 action particularly requires consideration here, because it affected 

 the successive adjustments and readjustments of material in the 

 planetary cores. It will suffice to consider merely the case of the 

 earth and the most typical agencies that affected it. The three 

 agencies that lie back of changes of rotation, of nutation, and of the 

 tides will sufficiently represent the whole. These agencies — and 

 those of their kind here neglected— arose out of the same general 

 processes as the planetary series itself and came gradually into func- 

 tion as the planets themselves took form. They were more or less 

 effective at all stages thereafter. One special effect was to bring 

 into play the resources that lay in the mass-coherence of solids, 

 an essentially new element in the evolution. 



The forces that produced the tides, the polar nutations and the 

 changes in rate of rotation, not only caused changes of form that 

 involved variations in the internal capacity of such inclosed 

 spaces as there may have been, but caused differential stresses to 

 permeate the growing cores from surface to center and call into 

 action the viselike capabilities of stresses greater below than 

 above. Those agencies which give rise to deformations of the 



