Report Intended to Illustrate a Map of the Hydrographical Basin of the Upper Mississippi River (Paperback)

This historic book may have numerous typos and missing text. Purchasers can download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1845 Excerpt: ... charged with carbonic acid. A weathering of this sort is accordingly observed on both sides of the Mississippi, on a distance of eight miles, from St. Peter's to the Falls of St. Anthony; at which latter spot it takes place to a greater extent. The underlying sandstone, being very friable, is easily acted on by meteoric and atmospheric agencies. The first effect of these is to form excavations in the sandstone, which, crumbling in, carries along the superincumbent limestone thus deprived of its support. In ascending the Mississippi in this last-mentioned distance, the traveller is astonished to find its bed so little encumbered by the debris of this limestone; and at the St. Anthony, he is still more surprised not to find a larger accumulation of detritus at the foot of its falls. This is owing to the solvent properties of the water previously alluded to; so that I have not the least doubt that the limestone at one time covered an extensive tract of country, and that the waters reaching the sandstone, the result of this species of denudation has brought about the peculiar configuration of the surface in this region of country, as seen on the left bank of the Mississippi, going from the St. Peter's to Carver's cave, and over the whole district watered by La Hontan and Vermillion rivers, and other places. These causes of erosion are doubtless still in full activity, and hence I am inclined to think that the recession of the Falls of St. Anthony is much more rapid than is generally supposed. As it is possible to find elements for the measurement of this result, 1 made surveys of the locality in the month of March, 1839. I have appended to this report a chart of the falls, exhibiting diagrams of their dimensions at that time, which will enable future generatio...