22 WRITINGS OF JOSEPH HENRY. [1824- 



below its general level, by the great depressions, in which 

 are situated the waters of its principal lakes and rivers. 

 The most important depressions, as we have already ob- 

 served, are the basins of Lake Erie and Ontario, the valley 

 in which is situated the Oneida lake and the Mohawk river, 

 and that which contains the Hudson river and Lake Cham- 

 plain. The basins of Lake Erie and Ontario are only parts 

 of the immense St. Lawrence basin, which contains the five 

 great western lakes, and bounds a principal part of the 

 northern frontier of the Union. As this interesting depres- 

 sion of country is intimately connected with the topography 

 of this state, we will dwell a few moments on some of its 

 general features. Commencing at the Gulf of St. Lawrence 

 it extends almost to the head waters of the Mississippi, a 

 distance of nearly 1800 miles. In its whole depression it is 

 computed to contain 511,930 square miles of surface, 72,930 

 of which is covered with water. It may be described as con- 

 sisting of three great but unequal divisions; the upper, the 

 middle, and the lower sub-basins. The first of these is in 

 the form of a rhomb, and has an area of about 90,000 square 

 miles, more than one-fourth of which is occupied by the 

 waters of Lake Superior. The next, or middle sub-basin, 

 occupies a quadrangular area of at least 160,000 square miles, 

 and contains the three central lakes, viz: Huron, Michigan 

 and Erie, in its lowest depressions. The surface of the lower 

 sub-basin has an area of about 260,000 square miles, and is 

 covered in part by the waters of Lake Ontario and St. Law- 

 rence river. 



Lakes Michigan and Huron are immense chasms, the 

 bottoms of which, in some places, sink to the almost incredi- 

 ble depth of 1000 feet below their surface, and more than 

 300 feet below the level of the ocean. This is an interesting 

 fact in the physical geography of the country; as these 

 lakes are probably the lowest depressions on the continental 

 surface of the earth. The surface of Lake Erie is elevated 

 565 feet above the level of the Atlantic ocean, 76 below Lake 

 Superior, and 35 lower than the general level of Michigan 

 and Huron. Its bottom, which is seldom depressed more 



