ON THE UPPER MISSISSIPPI. 



503 



extending as far as the eye could reach, occupying a width of country from two to 

 three miles in extent. 



Leaving these mounds to the left, and proceeding in a northwesterly direction, 

 five miles further brought us to some picturesque exposures of Lower Sandstone and 

 Magnesian Limestone, projecting in rugged escarpments from the sides and summits 

 of the hills, giving to the latter a peculiar castellated appearance. Towards the 

 base of the hills, beds of sandstone were frequently exhibited, in nearly horizontal 

 stratification, separated from each other by intervening spaces covered with a rank 

 growth of coarse grass. 



Near by, we struck the Iowa opposite a deserted Winnebago village, and found 

 an old Indian trail leading up the stream. Following this between two and three 

 miles, we ascended the bluffs, which were found to have an elevation of upwards of 

 four hundred feet. They consist of the prevailing rocks of the country, — Lower 

 Sandstone and Magnesian Limestone ; the beds of the latter formation being much 

 broken, and traversed by numerous fissures. The superior strata are mixed with 

 much chert, and contain numerous cavities filled with calcareous spar. 



Near this vicinity Messrs. Hatfield and Clayton found small quantities of lead 

 ore, and raised about a thousand pounds. 



Resuming our route down the Mississippi, I found the bluffs at Cap a Lai, of 

 Sandstone and Lower Magnesian Limestone, four hundred and fifty feet high ; and, 

 a short distance below this, on Section 4, of Fractional Township 99 north, we 

 found, near the water's edge, the third Trilobite bed of F. 1, with its characteristic 

 fossils. 



Escarpments of Lower Magnesian Limestone, based on sandstone, continue for 

 several miles on the west side of the Mississippi, with an elevation of four hundred 

 to four hundred and fifty feet. 



In the southeast corner of Fractional Section 6, of Township 97, the altitude of 

 the bluff is three hundred and forty-five feet. For the first one hundred and eighty 

 feet, ledges of sandstone, F. 1, are partially exposed ; over this rests : 



Feet. 



1. Thin-bedded magnesian limestone, possessing an oolitic structure, . 1)5 



2. Cherty beds, with concentric markings, .... 1 



3. Oolitic magnesian limestone, . . . . ... 2 



■i. Alternations of magnesian limestone and sandstone, ... 6 

 5. Escarpment of heavy-bedded magnesian limestone, . . . 144 



After passing the last exposure, the bluffs recede from the river, being separated 

 from it by a nearly level bench of bottom land, half a mile wide, through Fractional 

 Sections 7 and 18, Township 97, Range 2 west, and 13, 24, and 26, of Town- 

 ship 97, Range 3 west. 



At the point known as Painted Rock, situated in the southeast corner of Section 

 3, Township 96, Range 3 west, the bluff is three hundred and seventy feet above 

 the water-level, and affords a good section of the beds of Lower Magnesian Lime- 

 stone, resting on about one hundred and forty-five feet of white and yellow sand- 

 stone, projecting at intervals from the slope. The oolitic beds are here one hundred 



