the Earth's Contraction from Cooling. 371 



I find no explanation in the present state of science where- 

 fore most of the dry land of the globe should have been located 

 about the north pole, and of the water about the south. Physi- 

 cists say that it indicates greater attraction, and therefore a greater 

 density, in the solid material beneath the southern ocean. But 

 why the mineral ingredients should have been so gathered about 

 the south pole as to give the crust there greater density is the 

 unanswered query. It may be that magnetite is much more 

 abundantly diffused through the antarctic crust than the arctic. 

 This is only one of many possibilities, and it is at present with- 

 out a satisfactory fact to stand upon, beyond the general truth 

 that iron was universally present. 



6. Resulting Crystalline Texture of the Crust, 

 The doleritic and trachytic rocks of the true crust, and what- 

 ever else exists in its constitution, cannot be present with just 

 the texture we find in the rocks of existing dykes and volcanic 

 mountains. For, as above stated, the crust has cooled with in- 

 conceivable slowness, far more extreme than that which has at- 

 tended the formation of any of the coarsest granites and syenites. 

 And since the coarseness of crystallizations is generally in pro- 

 portion to slowness of cooling, the texture of the whole should 

 have been after the character of the coarse Archsean syenite or 

 hyposyenite and vein- granite, or else in much larger crystalliza- 

 tions. One or another of the cleavable felspars is, in all proba- 

 bility, everywhere present; and since the cooling, and therefore 

 the crystallization, has been in progress through many millions 

 of years and still goes on, the probability is that the felspar 

 crystallizations and cleavage-planes of the first-formed crust- 

 layer were lengthened downward for very long distances, if not 

 indefinitely. If so, the existence of a cleavage-structure in the 

 crust as courses of easiest fracture, such as I have appealed to 

 elsewhere in explaining the origin of the courses in the earth's 

 great feature-lines*, is not an unreasonable supposition* 



7. The Continents always the Continental Areas. 

 The above-stated effects of contraction lead to the necessary 

 conclusion that the oceanic and continental areas were defined 

 when the earth's crust first began to form— if not also still earlier, 

 during the progress of its nucleal solidification. It is hardly 

 possible to conceive of any conditions of the contracting forces 

 that should have allowed of the continents and oceans in after 

 time changing places, or of oceans as deep nearly as existing 

 oceansbeing made where are now the continental areas, — although 

 it is a necessary incident to the system of things that the con- 



* Sillimau's American Journal (II.), vol. iii. p. 381 (1847). 

 2C2 



