309 



of this bari'ier, or the continuance of the elevatoiy movement, closed 

 up the communication by way of the Mississippi Yalley, a body of wa- 

 ter would remain, filHng nearly the whole " basin of the St. Lawrence," 

 and receiving constant accessions from the streams which discharge into 

 it. 



At this period, we may conclude, the rocky barriers of the Mohawk 

 and Hudson, unable to resist the enormous pressure of the accumulating 

 volume, gave way, discharging the surplus waters with tremendous vio- 

 lence, and thus opening a passage for the present gi'eat channels of 

 water communication with the ocean, through the State of New 

 York. 



Subsequent to this event, the continued uplifting of the land, or the 

 bursting of the barrier of the AUeghanies, opened a passage for the 

 waters through their present outlet of the St. Lawrence, when Lake 

 Erie and the upper lakes subsided to about their present levels. Then, 

 for the first time, their accnmulated watere, confined by the valley of 

 the Niagara, rushed over its " wave-worn precipice," producing that stu- 

 pendous cataract, which now seems likely, for ages, to emit its unceasing 

 thundere. 



. The "lake-ridge," of New York, may be considered as the shore of 

 Ontario, after this parting of the lakes had taken place, and must nec- 

 essarily be of subsequent formation to those of Lake Erie. A still 

 further progress of the elevation afterwards, alone, would reduce that 

 lake to its present level, without affecting the levels of the upper lakes. 



It is not our design, nor would it come within the scope of this re- 

 port, to discuss the prime cause of these ai'eat changes. We rest here 

 on the assurance that it involves no principle which a geologist, at this 

 day will deny. A fact is mentioned by Prof. Emmons, in the first 

 Geological Report of New York, which has so immediate a bearing on 

 the principle here made use of, that I cannot refrain from alluding to 

 it. It is this — "That the waters of the St. Lawrence are declining, or 

 do not appear at so high a level now as formerly ; oi-, v?hat is about the 

 same thing, the country is rising." "The possibility of such a change," 

 he justly remarks, "can no longer be doubted, since it is clearly 

 proved that portions of the continent of Europe are now undergoing 

 the same change. Norway is gradually rising, and Greenland is grad- 

 ually sinking." Similar phenomena are also taking place on the west- 



