484 DESCRIPTION OF THE COUNTRY BORDERING 
Feet. Inches. 
4. Seam of grayish oolitic chert, with a thin incrustation of whitish decom- 
posing chert, . 2 to3 
5. Light salmon-coloured magnesian Lineihenk: — Peeere siethanin, 
and cavities lined with crystals of calcareous spar, in layers from 
a few inches to two fect in thickness, containing Lingulz, Orthis, 
and Trilobites, . ‘ ‘ ‘ : ‘ 11 
The magnesian limestone at this locality does not differ essentially in appearance 
from that noticed near Abert’s Run.* It contains two kinds of Lingulez; one, an 
elegant little species, of an ovate shape, with fine concentric striz, is not distin- 
guishable from Lingula Dacotaensis, a form which characterizes the Lower Magne- 
sian Limestone, at the quarry near Stillwater, and other localities throughout the 
Chippewa Land District; the other, of which we obtained only a few fragments, is 
much larger, but the specimens are so imperfect, that the characters of the species 
cannot be made out. Associated with these Lingulze, we found the cast of a small 
Orthis, with fine radiating strise, and portions of the cephalothorax of a Trilobite, 
related to the family Olenide. 
Between White Rock and Traverse des Sioux, the land is high and rolling, and, 
in general, well timbered with elm, oak, hard and soft maple, white and black 
walnut, ash, and linden. The banks of the river are, usually, from eight to ten 
feet high. 
Boulders, chiefly of granite, syenite, and porphyritic and greenstone trap, occur 
in great profusion, scattered over the surface of the upland prairie, but we did not 
notice any exposures of stratified rocks. The Lower Sandstone, F. 1, doubtless 
forms the nucleus of the hills, since, in digging a well at Traverse des Sioux, near 
_the house of the Rev. Mr. Hopkins, thirty feet above the river, this rock was struck 
a few feet below the surface. And one mile beyond Traverse des Sioux, the same 
sandstone appears in the bed of the river. The rock is rather fine-grained, of a 
light buff colour, and has numerous brown spots disseminated. It is more compact 
than the sandstone occurring at White Rock. One of the layers is highly charged 
with casts of Huomphalus Minnesotensis. 
Two miles above Traverse des Sioux, the sandstone exhibits a nearly perpendi- 
cular face of twenty feet, towards the river; and two miles still further up it forms 
solid ledges, twenty-five feet thick, capped with twenty feet of magnesian limestone. 
In the sandstone we found with the above Euomphalus, the pygidium of a small 
Trilobite, but the rock was of such a friable character, that we were not able to pre- 
serve specimens. The magnesian limestone contains Lingula Dacotaensis, and 
remains of a species of Trilobite, apparently identical with that occurring at White 
k. We could not perceive any dip in the strata at this section. 
* The composition of this magnesian limestone is as follows : 
Carbonate of lime, . : ; : : : : 58-65 
Carbonate of magnesia, ; : : : : ; 29°15 
Insoluble matter, .- ; : ‘ ; 7-25 
Alumina, oxide of iron, and aninienet: : : : j 1:35 
Water, : s : : P . : 2-65 
Loss, : ’ ‘ ; ‘ ‘ : ; 0-75 
100-00 
