VII] ON SOME POINTS IN DYNAMICAL GEOLOGY. 71 



sions of Hopkins and others as to a solid globe, I have been 

 endeavoring, since 1858, to reconstruct, in the language of Pro- 

 fessor LeConte, " the theory of igneous agencies on the basis of a 

 solid earth." Alone up to this' time, so far as I am aware, I 

 have labored to expand, complete, and give geological and 

 chemical consistency to the suggestion long since put forth, 

 both by Keferstein and by Sir John Herschel, that the deeply 

 buried and water-impregnated strata between the superficial 

 crust of the earth and the solid nucleus constitute a region " of 

 plastic material adequate to explain all the phenomena hitherto 

 ascribed to a fluid nucleus," since " any changes in volume re- 

 sulting from the contraction of the (solid) nucleus would affect 

 the outer crust through the medium of the more or less plastic 

 zone of sediments precisely as if the whole interior of the globe 

 were liquid." 



A softening by heat of previously solid porous sediments, 

 filled with water, was maintained (in accordance with the views 

 of Babbage as to the rise of the isogeothermal horizons from 

 the deposition of newer strata) to depend upon the accumula- 

 tion of large thicknesses of sediment, the results of which heat 

 and softening were declared by me to offer a " ready explana- 

 tion of all the phenomena of volcanoes and igneous rocks." This 

 relation of volcanic phenomena to great acccumulation, and of 

 those of recent times to more modern sedimentary deposits, 

 which was also maintained by me, was subsequently insisted 

 upon and enforced by Professor James Hall in the introduction 

 to the third volume of the Paleontology of New York. A sum- 

 ming up of these views as put forth by me in March, 1858, and 

 in November, 1859, will be found in the American Journal of 

 Science for May, 1861. (See Essays I., II., and V. of the present 

 volume.) In this last it was shown, in opposition to the no- 

 tion of Babbage (who had speculated upon the expansion and 

 consequent elevation of the deeply buried strata by heat), that 

 one of the effects of heat and water upon the buried sediments 

 would be condensation, from the diminution of porosity and 

 still more from the conversion of the earthy materials into 

 crystalline species of higher specific gravity, thus causing con- 



