The inland route to the sources of the Mississippi, and adjacent regions, is by the channel of the latter. The following distances and relative elevations from the Fond du Lac, or mouth of St. Louis river, to the sources of the Mississippi, are extracted from Schooleraft's travels with Governor Casst.
We thus find the extreme summit level, between Lake Superior and Sandy lake, to be 550 6 feet above the sur face of the former, in a direct distance of about 70 miles. If this estimate is correct, the country west of lake Su perior has a rise, in 70 miles, of within 90.4 feet as much as from tide water in the Hudson to the head of that lake.
Depression from the summit level to Sandy lake : Dep. Feet.
To first Rapid, . . - - - 2 Descent of the rapid, llead of second rapid, 4 11 Descent of do. 8 19 Thence to the level of Sandy lake, - - - 4 6 23 6 This depreasion taken from 550 6 feet leaves 527 feet. as the elevation of the surface of Sandy lake over that of lake Superior. Mr. Schoolcraft (page '261) estimates the entire fall from the summit level through Sandy Lake into the Mississippi at 60 feet ; ancl the elevation of the sources of that river, above that of the mouth of Sandy Lake river, at 162 feet.
From these elements we have 36.4 feet fall from San dy lake into the Mississippi, yielding an elevation of that stream at the mouth of Sandy Lake river, above the sur face ()flake Superior, of 490.6 feet. If to the latter sum \VC add 162 feet, WC have 652.6 feet as the elevation of the sources of .Mississippi river above the surface of lake Superior. We have already found that the latter lake was elevated 641 feet above the Atlantic tides, which sum added to 652.6 produces 1293.6, say in round rumbers 1,300 feet, as the elevation of the sources of the Mississippi over the Atlantic tides ; (see article :NIississippi, page 627, in the note.) In that note it will be seen that Mr. Schoolcraft's deduction does not agree with his elements. He there deduces 1330 feet as the elevation of the Mississippi sources :—But by adding together 641 feet the elevation of lake Superior, 550.6 feet rise to the intermediate summit level between lake Superior, and the mouth of Sandy-lake river, and 162 feet as the rise of the Mississippi river from Sandy-lake river to its sources, we have 1353.6 feet ; and this sum,
less 60 feet, the fall from the summit level before no ticed, to the mouth of Sandy-lake river, leaves as before 1293.6 feet as the real elevation of the sources of the By the river of the Grand Portage, which enters lake Superior nearly opposite to the south-west end of Isle Royal, a route is opened with the wide uncultivated ex panse upon the sources of the Winnepeg, Assiniboin, Red, and other branches of Saskashawin. This is the great thoroughfare of the fur trade.
The enormous surplus mass of the waters of lake Su perior are dis.charged at the falls of St. NIary, North Lat. 46° 31', by a fall of 22 feet 10 inches, according to the admeasurement made by Col. Gratiot.* The river, or strait of St. Mary's is about 40 miles in length, and connects the upper secondary basin of St. Lawrence with that of Lake Huron. Michigan, Erie, and their con fluent waters. The latter basin, depressed below the former 76 feet, spreads over a parallelogram of 500 by 400 miles ; or embracing a superficies of 200,000 square miles. Of this extent, lake Huron occupies 20,000 square miles, Michigan 13,500, and Erie 15,000, or over an aggregate of 48,500 square miles. If to this we add 7.500 square miles for lakes St. Clair and Nipissing, other smaller lakes, and the rivers, we have, in round numbers, in the second or middle basin of St. Lawrence, 50,000 square miles of water, or one fourth part of the entire surface.
The middle is the most valuable of the three minor basins of St. Lawrence. In point of climate, it reaches from North Lat. 40° 20' to North Lat. 47°. The arable surface is unequally divided, as near two thirds of the whole is on the right or United States side of the chain of lakes. It would be needless to enumerate the great number of rivers which every where flow from the ad jacent country into the lakes : we will therefore particu larly notice only these which from their position have already, or may become noted channels of Inland Na‘i gation.