Wishing to deviate as little as possible from the course we had assumed, and which we knew it was necessary to pursue, if we would follow the most {105} direct route to Council Bluff, we descended on the 19th, into a broad and densely wooded valley on our left. After crossing a part of this valley, through heavy forests of ash, sycamore, and cotton-wood, our progress was checked by a river of some magnitude, and so swollen and turbulent in consequence of the late rains, that we thought it advisable not to attempt the passage. We therefore relinquished our course; and being a long time detained in painful and fatiguing exertions to extricate ourselves from the forest, regained towards evening the open plain, and encamped. We had now ascended about eighty miles from the mouth of Grand river. The country we had passed is fertile, and presents such an intermixture of forests and grassy plains, as is extremely pleasing to the eye. Towards the north the hills became gradually more and more elevated. The discontinuance of the horizontal limestone, the disclosure in the deep vallies of the more ancient varieties of sandstone, and the frequent occurrence in the soil of small round masses of granite, gneiss, and other primitive rocks, indicate an approach towards the margin of the secondary basin. In the deepest vallies, about the sources of Grand river, we observe a very hard semi-crystalline sandstone, in rather indistinct strata, and containing apparently few remains either of plants or animals. It is, in almost every respect, similar to that sandstone, which, in the valley of Lake Champlain, rests along the skirts of the granitic mountains of Ticonderoga, Crown Point, and Westport, and supports there a small stratum of compact limestone. Containing few fragments rounded by attrition, being almost destitute of cement, and retaining much uniformity of character in different localities, it has a manifest resemblance to that most ancient of sandstones, which, in the mountains of New England, is associated with the granular limestone, and has sometimes been called {106} granular quartz.[65] Indeed we have no hesitation in believing, that at some point near the sources of the De Moyen and Grand river, the primitive rocks approach near the surface. There is here a stratum of newer sandstone, superimposed upon that above noticed, and bearing marks of having been contemporaneous to some formation of coal; but it is not of sufficient thickness, in the parts we examined, to justify an opinion, that it contains any valuable beds of that mineral. Leaving the immediate neighbourhood of the river, there is an ascent of several miles to the level of the great woodless plain. The bottom, and part of the sides of the vallies, are covered with trees; but in proportion to the elevation, the surface becomes more unvaried and monotonous. These vast plains, in which the eye finds no object to rest upon, are at