GEOLOGY. 245 



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epochs, of the plains of Northern Germany as well as a great part of 

 Scandinavia and on this continent, the coast of the United States, 

 from Florida to Canada, formed a series of banks and shoals like the 

 Banks of Newfoundland in our day, whilst the plains of the West, 

 between the Alleghanies and the Rocky Mountains, formed a vast bay, 

 comparable to the Gulf of Mexico, in which the sea deposited the 

 fine sand and clay of the prairies, as it now deposits in the Gulf of 

 Mexico the sand and mud that border the coast of Texas." 



In conclusion, Mr. Desor remarks, that the sedimentary deposits of 

 the most recent geological epochs, being, in all respects, like the 

 alluvial deposits of our day, it is probable that they were formed un- 

 der the operation of the same laws ; and that the form and extent of 

 continents, so far as they are composed of sedimentary deposits, are 

 thus dependent on astronomical laws, that is, on the attraction 

 which the sun and moon exert, and in all time have exerted, on the 

 liquid part of our planet. 



ON THE PHENOMENA OF THE RISE AND FALL OF THE WATERS 



OF THE NORTHERN LAKES. 



AT a meeting of the American Academy, February, 1849, Mr. 

 Foster, of the United States Mineral Survey in the Northwest Ter- 

 ritory, presented the result of some observations undertaken with a 

 view of determining whether the w 7 aters of the Northern lakes are 

 subject to any movements corresponding to tidal action. The result 

 of these observations had convinced him that these waters do not rise 

 and fall at stated periods, corresponding to the ebb and flow of the 

 tide, but are subject to extraordinary risings, which are independent 

 of the influence of the sun and moon. These risings attracted the 

 attention of the earliest loyageurs in these regions. Charlevoix, who 

 traversed the lakes nearly a century ago, says, in reference to Lake 

 Ontario, " I observed that in this lake there is a sort of reflux 

 and flux, almost instantaneous ; the rocks near the banks being cov- 

 ered with water and uncovered again several times in the space of a 

 quarter of an hour, even if the surface of the lake \vas very calm, 

 with scarce a breath of air. After reflecting some time on this ap- 

 pearance, / imagined it was owing to springs at the bottom of the lake, 

 and to the shock of their currents with those of the rivers which fall into 

 them from all sides, and thus produce those intermitting motions." The 

 same movements were noticed by Mackenzie, in 1789 ; by an expe- 

 dition under Col. Bradstreet, in 1764 ; on Lake Erie in 1823, and at 

 various later periods. In the summer of 1834 an extraordinary retro- 

 cession of the waters of Lake Superior took place at the outlet of 

 Sault St. Marie. The river at this place is nearly a mile wide, and 

 in the distance of a mile falls 18.5 feet. The phenomena occurred 

 about noon. The day was calm, but cloudy. The water retired sud- 

 denly, leaving the bed of the river bare, except for a distance of thirty 

 rods, and remained so for nearly an hour. Persons went out and 

 caught fish in pools formed in the depressions of the rocks. The return 

 of the waters is represented as having been very grand. They came 



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