GEOLOGY. 253 



Rivpr, he has soen a large bank of shells filled with specimens of 

 shells which he believes will prove to l)e of living species. 



Passing t'roni the continent to Formosa, Castle Zclandia, a fort 

 built by the Dutch in IGoi, on what was then an island, is now 

 some distance l)aclv from the river and in th(i centre of the city of 

 Taiwan f u ; also at Takao, recent crabs and recent shells are 

 founti at a height of 1,111 feet above the present level of lh(; sea. 



Passing over to Niphon, we find on the western side of the Bay 

 of Yedo, a plateau some 200 feet high, its top as level as if made 

 by the hand of man. A short journey from Yokohama back to 

 Kanasawa, hence across to the Bay of Kamokura, and up the 

 Tocaido to Kanagawa, shows that all this area is also of very re- 

 cent marine origin. 



North of Niphon, on the Island of Yesso, terraces line the 

 northern shore of Tsugar Strait and Volcano Bay, and what has 

 already been described in Corea, again appears there, but on a 

 much frrander scale. The greatest heifrht to which he has been 

 able to trace the recent action of the sea is 1,180 feet. This was 

 found on the flanks of the mountains north of Hakodadi. 



All these facts considered in connection with the dry beds of 

 friths and bays along the Siberian borders of the Arctic Ocean, 

 and the remnants of the old gulf that once washed the eastern 

 flanks of the Ural, give some idea of how the Asiatic continent 

 has increased her area within the later geologic times. 



THE UPPER MISSISSIPPI. 



Gen. Warren, of the U. S. Engineers, read a paper, at the 1868 

 meeting of the American Association, on certain features of the 

 Upper Mississippi. 



He had been struck by the immense excavations made by the 

 river in the Silurian rocks; eff'ects which could not be produced by 

 the present stream, even when swollen by the greatest rains. 

 Some parts of the bed for 200 miles are granitic. Above the Minne- 

 sota on the Mississippi is a region which is evidently an extensive 

 lake, which extends to Lakes Winnij^eg and Winnipiseogee. 



Lake Winnipeg is about 650 feet above the ocean level, while 

 some i^arts of this old lake bed are 1,000 feet above the sea, — ac- 

 cording to Mr. Hines. 



The question arose how the outlet was changed from a northern 

 to a southern one. The glacial epoch could hardly account for it. 

 Probably there was a continental oscillation which caused this 

 great change. When the bed of the lake was raised the water 

 flowed over toward the north and south, wearing away the adja- 

 cent formations. The evidence of a northern depression is shown 

 by the conformation of the great lakes, the outlet of Lake Michi- 

 gan formerly having been at the south end. Lake Winnebago 

 anciently was much larger than now, and had a different outlet. 

 It was thought that this continental oscillation was still going on, 

 causing a depression on the Atlantic coast, and extending from 

 the Mississippi to Greenland, tending to elevate the south-westeru 

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