of Lake Superior. ^, 



of the river St. Louis, at the Fond du Lac. The greatest breadth 

 is opposite Peek Island, and is 140 miles. The sum of the courses 

 round the lake is 1155 miles, always avoiding the bays, especially 

 Black Bay, which is itself about 90 miles around. 



This body of water may be considered to be 617^ feet above 

 the surface of the Atlantic, and 52| feet above Lake Erie*; of 

 these 52| feet, 30 are generally allowed to be the difference of 

 elevation between Lakes Erie and Huron, and 22J have been 

 allotted to the ascent from Lake Huron to Lake Superior ; viz.^ 

 four feet, by Major Long's t estimate, at the Nibish and Sugar 

 Rapids, at either end of Lake George, and 18| feet at the Falls 

 of St. Mary, as measured lately by the engineers of the United 

 States. 



From all I can gather, no gradual diminution is taking place in 

 the quantity of the water of Lake Superior. The contrary, in 

 truth, might be presumed, from its receiving the contents of 220 

 rivers and brooks, some of great size, and from its possessing only 

 one outlet. Sixty years, however, have produced no change at 

 the Grand Portage, where such an event would be readily de- 

 tected. The appearances on the coast indicating a drainage are 

 owing to temporary and local elevations and depressions, caused 

 by storms ; and to the fluctuations attributable to the seasons. 

 The effect of tempests in raising the level of certain parts of the 

 lake is very considerable. In autumn, a westerly gale, lasting 

 more than a day, will sometimes inundate the site of the store- 

 houses of the Hudson's Bay Company, at the Portage of the Falls 

 of St. Mary ; and will raise the water 20 or 30 feet at Gargantua, 

 Michipicoton, or the Otter's Head, places exposed to the accu- 

 mulated force of waves travelling over 200 or 250 miles of un- 

 obstructed and deep water. 



Respecting the depth of Lake Superior, I have little to offer. 

 It is doubtless very deep, judging from the coldness of its 



* Determined to be 56.5 feet above the tide water on the river Hudson, by 

 order of the Commissioners of the Great Western Canal of New York. 



t- Of the United States' topographical engineers, and commander of several 

 exploratory cxi)cdilions. 



B 2 



