Upon the St. Louis River there is exhaustless water-power,--a descent of five hundred feet, with a stream always pouring an abundant flood. Its source is among the lakes of northern Minnesota, which, being filled to overflowing by the rains of spring and early summer, become great reservoirs. With such a supply of water there is no locality more favorably situated for the manufacture of every variety of domestic articles. Undoubtedly the water-power will be largely employed for flouring-mills. The climate is admirably adapted to the grinding of grain. The falls being so near the lake, there will be cheap transportation eastward to Buffalo, Cleveland, Philadelphia, New York, and Boston, while westward are the prairies, easily reached by the railroads. The geological formation on the north side of Lake Superior is granite, but as we follow up the St. Louis River we come upon a ridge of slate. It forms the backbone of the divide between the lake and the Mississippi River. A quarry has been opened from which slates of a quality not inferior to those of Vermont are obtained, and so far as we know it is the only quarry in the Northwest. It is almost invaluable, for Nebraska, Kansas, Iowa, western Minnesota, and Dakota have very little wood. Shingles are costly, but here is abundant material to cover the roofs of the millions of houses that are yet to rise upon the prairies. This slate formation is thus referred to by Thomas Clark, State Geologist, in his Report to the Governor of Minnesota, dated December, 1864 (pp. 29, 30):--