XI. 



THE OUTLINES OF LAKE SUPERIOR. 



SINCE it has been ascertained that the present form of the surface 

 of our globe, and the distribution of land and water and their rela- 

 tive level, and the general outline of their contact, is the result of 

 the successive geological changes which our globe has undergone, 

 the efforts of geologists have more or less had in view to ascertain 

 the order of succession of these phenomena, and their mutual depen- 

 dence. One result is already established beyond question, namely, 

 that the changes which have brought about the present physical 

 state of our globe have been successive and gradual, and have 

 followed each other at more or less remote epochs. So that its pres- 

 ent configuration, far from being the result of one creative act, must 

 be considered as the combination of a series of successive changes ; 

 fa from being moulded like a bell at one furnace, it has been built 

 up by successive superstructures. This is not merely a view adopted 

 in accordance with our theories and preferences, but it is actually 

 shown by geological evidence, that the solid parts which constitute 

 the crust of our globe have been consolidated at different epochs, 

 and have been lifted to the surface above the level of the sea at long 

 distant intervals ; so that continents are known to have been built 

 up by the successive rise of groups of islands, combining, by their 

 gradual elevation above the level of the sea, into larger tracts of 

 main land, until they have assumed their present definite outline and 

 general relations. 



The modes in which these changes have taken place have been 

 quite diversified. We have indications of large tracts of land ex- 

 tending in horizontal continuity over great extents at considerable 

 heights above the level of the sea. 



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