"Brick Kilns," Clay Bluffs 1900 Miles above St. Louis

By the action of water, or other power, the country seems to have been graded away; leaving occasionally a solitary mound or bluff, rising in a conical form to the height of two or three hundred feet, generally pointed or rounded at the top, and in some places grouped together in great numbers . . . the sides of these conical bluffs (which are composed of strata of different coloured clays), are continually washing down by the effect of the rains and melting of the frost; and the superincumbent masses of pumice and basalt are crumbling off, and falling down to their bases . . . The strata of clay are alternating from red to yellow-white-brown and dark blue; and so curiously arranged, as to form the most pleasing and singular effects.” George Catlin painted this work in 1832 on his first extended voyage up the Missouri River. (Catlin, Letters and Notes, vol. 1, no. 10, 1841; reprint 1973)