74 PROTOZOIC ROCKS 
The shell-beds, with some alternations of marly clays, form the base of these 
singularly shaped hills, capped with harder, more magnesian, and less fossiliferous 
layers. 
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SYMMETRICAL FORM OF HILLS, TURKEY RnRiveER. 
Below the principal forks of Turkey River, the fossiliferous strata appear only 
in low mural exposures, a few feet above the river, while the higher magnesian 
beds protrude from out the grassy slopes above in a variety of curious and fantastic 
shapes, and often in the buttress-like form represented on the opposite page. 
The heights of Fort Snelling command an extensive prospect, both up the valley 
of the St. Peter’s River, over the surrounding country towards the Falls of St. 
Anthony, and on the opposite side of the Mississippi. In all directions, as far as 
the eye can reach, a vast stretch of gently undulating prairie is in view, supporting 
a calcareous soil, which for upland is of excellent quality, and remarkable for the 
heavy crops of oats which it produces. While the greater portion of this soil is 
based on lower ledges of the limestone formation under consideration, with more 
or less thickness of drift intervening, other limited tracts rest upon a white shell 
marl and other infusorial earth, possessing fertilizing properties. 
Timber is scarce on this part of the Upper Mississippi, being limited chiefly to 
narrow belts along the water-courses; the country adjacent to the Mississippi 
could, however, easily be supplied with wood, procured higher up on this river; 
or, if inhabited by a provident people, plantations would soon spread over the this 
of the country. 
