"These slates are found in all degrees of character, from the common indurated argillaceous fissile to the highly metamorphosed and even trappous type. The working of these slates demands the attention of builders; their real value is economically of more importance to the prairie and sparsely timbered valley of the Mississippi than any other deposit in the State's possession on the lake. The annual draught of hundreds of millions of lumber upon the pine forests of the St. Croix and Upper Mississippi and tributaries will exhaust those regions before the close of this century. The trustees of our young Commonwealth are emphatically admonished to encourage and foster the working of these slates, and to bring them into use at the earliest time possible. A hundred square feet of dressed slates at the quarries of Vermont, New York, and Canada are worth from one and a half to two dollars; the weight ranges from four to six hundred pounds, or about four squares to the ton. A ton of this roofing may be transported from the St. Louis quarry to the Mississippi, by railway, at three dollars, and thence by river to the landings as far down as St. Louis or Cairo; but the article may be at all points in this State accessible by boats or railway, at an average cost of fifteen dollars per ton, or, at most, four dollars per square,--little, if any, more than pine shingles; the former as good for a century as the latter is for a decade. The supply of these cliffs is literally inexhaustible; if one fourth of this slate area in the St. Louis Valley proves available,--and doubtless one half will,--it will yield one thousand millions of tons. "The demand for this slate at ten roofs to the square mile, and for forty thousand square miles, would be one million of tons, or one thousandth part of the material. The annual demand for slates in the Mississippi Valley may be reasonably estimated at one hundred thousand tons, an exportable product of two hundred thousand dollars, besides the element of a permanent income to the railways and water-craft of the State of a half-million of dollars annually." To-day the country along the St. Louis is a wilderness. Climb the hills, and look upon the scene, and think of the coming years. "Thou shalt look Upon the green and rolling forest tops, And down into the secrets of the glens And streams, that with their bordering thickets strive To hide their windings. Thou shalt gaze at once, Here on white villages, and tilth and herds, And swarming roads, and there on solitudes That only hear the torrent, and the wind, And eagle's shriek." Here, through the bygone centuries, the Indians have set their nets and hooks without ever dreaming of laying their hands upon the wealth that Nature has ever in store for those who will labor for it.