100 Topographical Sketch of the State of Neic-Yorlc. 



of about 260,000 square miles, and is covered in part by the wa- 

 ters of Lake Ontario and St. Lawrence river. 



Lakes Michigan and Huron are immense chasms, the bottoms of 

 which, in some places, sink to the almost incredible 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 than 200 

 feet below its surface, is composed of alluvial deposit, probably 

 washed down from the upper lakes by the continued action of a 

 rapid current. Lake Ontario is elevated 231 feet above the level 

 of the ocean : its mean depth has been estimated at 492 feet, al- 

 though, in the middle, attempts have been made with 300 fathoms 

 without striking soundings* The St. Lawrence river, which con- 

 nects this system of lakes with the Atlantic ocean, is the second 

 river in magnitude in America, being no less than ninety miles 

 wide at its mouth, and navigable for ships of the largest size, 400 

 miles from the ocean : Its whole length, from Lake Ontario to its 

 mouth, is 692 miles.t 



The following table, compiled from Darby's Geographical View 

 of the United States, gives in a connected form, the elevation and 

 extent of the several waters of the St. Lawrence basin. 



No. X. 



Table of Elevation, mean Depth, Length, Breadth and Area, of 

 the several collections of Water in the great St. Lawrence basin. 



* Dr. Bigsby's sketch of the topography of Lake Ontario. Philo^oph. Mag. and 

 Annals, yoi. S, page 4. * t Darby. 



