Dr. Forry on the Climate of the United States, Sf'c. 21 



try." Presuming that our readers are sufficiently well acquainted, 

 for the present purpose, with the physical features of the vast 

 region stretching from the Atlantic to the Pacific, and from the 

 Gulf of Mexico to the inland seas on our northern frontiers, the 

 descriptions will be limited to such parts alone as are essential. 



One of the most striking characteristics of the physical geogra- 

 phy of the United States, and which, it will be seen, induces the 

 most remarkable modifications of climate, is the existence of those 

 great inland basins of water which lie on our northern frontier. 

 Of so vast an extent are these ocean-lakes, that one of them 

 (Lake Superior) has a circuit, following the sinuosities of the 

 coast, of 1,750 miles. The basin of the St. Lawrence is truly a 

 region of "broad rivers and streams," containing, it is estimated, 

 an area of 400,000 square miles, of which 94,000 are covered 

 with water. From the western extremity of Lake Superior to 

 the Gulf of St. Lawrence, the distance is about 1,900 miles. 

 These oce.an-lakes have been estimated to contain 11,300 cubic 

 miles of water, — a quantity supposed to exceed more than half of 

 all the fresh water on the face of the globe. The deepest chasms 

 on the surface of either continent are presented perhaps by the 

 depression of these lakes ; for though elevated near 600 feet 

 above, the bottom of some is as far beneath, the level of the 

 ocean. Lakes Huron and Michigan, which have the deepest 

 chasms, have been sounded to the amazing depth of 1,800 feet 

 without discovering bottom. 



The following table, which gives the mean length, breadth, 

 depth, area, and elevation of these several collections of water, 

 is taken from a recent report made by Douglas Houghton, Esq., 

 state geologist of Michigan. 



