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PROCEEDINGS OF THE GEOLOGICAL SOCIETY. 



[Apr. 9, 



of rivers here and there break through these rings ; and the rivers 

 themselves are also bordered with terraces. 



Such appearances, either continuing into the adjacent countries, 

 in the form of high plains, or sinking into swamps, constitute a far 

 more striking feature in these regions than in England. To measure 

 and delineate them would occupy a commission of geologists for 

 years. 



The deposits forming the terraces are composed of detritus, varying 

 throughout the valley of the St. Lawrence with the locality, — a cer- 

 tain kind being confined to a certain district. They are mostly de- 

 rived from the sub-rock, but mixed, as we have seen, with foreign 

 matters. 



This native debris, whether calcareous or metamorphic, is almost 

 invariably gritty, in sharp-edged, lenticular pieces, as if it had been 

 pounded. 



The terraces are the margins of former bodies of water, much 

 loftier and larger than those now existing. These ancient lakes have 

 been more or less emptied by the elevation of their beds, — an eleva- 

 tion taking place, perhaps, very extensively, slowly, and variously. 

 How and when the changes in level, — their degrees and sequences, — 

 took place, I do not pretend to say. 



Figs. 3 and 4 show the present levels of the region between Lake 

 Michigan and the Gulf of St. Lawrence, and of that between Lakes 

 Huron and Champlain. The lines of section taken are indicated on 

 the general Map, PI. XIV. These diagrams show also the positions 

 and elevations of some marine and freshwater deposits ; most of them 

 were discovered by our associate Mr. Logan, but that at Montreal 

 was first announced by the late Dr. Lyon, and that at Hull, on the 

 Ottawa, by myself. We hereby see, that the land with its terraces, 

 becomes higher as it recedes from the Atlantic ; the ancient banks of 

 Lake Superior being 930 feet above tide-water, which may or may 

 not identify the waters depositing them with the sea ; and thus they 

 may have covered the Canadas, United States, &c. 



These Lake Superior deposits, nevertheless, contain no organic 

 remains, as far as is yet known ; but, descending eastward into Lake 

 Huron, we find extensive fresh-water beds on its east shore, 614 feet 

 above the ocean ; and another (or others) a few feet lower, on the 

 river Detroit, on Lake Erie, and the river Niagara. 



Descending from Lake Erie to Lake Ontario, we have another 

 great set of concentric terrace-rings ; these also are destitute of or- 

 ganic remains, and are supposed to be marine by the State Geologists 

 of New York. 



Two hundred miles nearer the sea, Mr. Logan found on the Lower 

 Ottawa many and large deposits, side by side, both of fresh-water and 

 marine shells, spread over a space 150 miles in length ; and doubt- 

 lessly more are yet to be revealed, as clearances go on. 



The marine shells of Montreal Hill are 460 feet (470 feet, accord- 

 ing to Mr. Logan) above the sea — while about a mile on their south, 

 some hundred feet below, is a bed of fresh-water shells, in which the 

 horns of a large land-animal have been found. 



