GEOLOGY. 



THE ELEVATION OF CONTINENTS AND THE DEPRESSION OF SEA 



BASINS. 



It has already been shown, in a paper in the "Proceedings of 

 the Boston •Society of Natural History " for 18G6, that there are 

 good reasons for supposing that there is an essential ditierence 

 in the nature of the two series of plienomena of elevation, conti- 

 nents and mountain chains ; that they are entirely difl'erent in 

 character, and are not connected by a series of forms. An effort 

 has been made, in the paper referred to, to account for this dissimi- 

 larity by supposing that mountains are the product of the contrac- 

 tion in an outer crust in some way separated from the internal 

 mass, if that mass be solid or floating on it, if we accept the old 

 and now questionable theory of a molten interior. Pursuing the 

 same line of reasoning, it can be shown that the causes of the con- 

 tinental surfaces and the sea basins are due to the wrinkling of all 

 that portion of the earth which is called, even by those who do 

 not acknowledge the implication of internal fluidity, its crust. A 

 diminution of the earth's radius to the amount of four and a half 

 metres in 2,500 years, according to ISIayer, has resulted from loss 

 of heat. It has long been seen that the contraction must be 

 accompanied by a wrinkling of the crust, which, not losing heat, 

 or not losing it as rapidly as the internal mass, must adapt itself to 

 the diminished nucleus ; but as yet nothing has been done to deter- 

 mine the forces which cause certain parts of the crust to bend up 

 and others to bend down as this wrinkling goes on. The idea has 

 been generally prevalent among natiu*alists and geologists that the 

 position of these up and down curves of the crust of the earth is not 

 permanent, but that the continental curves may become flattened 

 out or even replaced by the depressions of the seas. This supposi- 

 tion is necessarily made by all those who, Ibllowing the distinguished 

 leader of our science. Sir Charles Lyell, call in such changes to 

 account lor alterations of climate and the destruction of organic 

 life. The following reasons militate against this view : — 



1st. When the contraction of the central mass has once thrown 

 the crust into ridges and furrows, that is, formed continents and 

 sea basins, all further contraction will necessarily temi to develop 

 these ridges and furrows ; nor can we legitimately sujipose that 

 these ridges and depressions have ever changed places, unless we 

 can show some cause competent to overcome the very great re- 

 sistmce which they must oppose to such change's. 



2d. The accumulation of sedimentary matter on the ocean floors 



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