166 FORMATIONS OF THE INTERIOR 
that I was able to gather of the circumstances of its discovery, I am led to believe 
that it has been transported from a distance. : 
Mr. Sloan, of Little Rock, informed me, that he had seen a piece of native copper, 
which was picked up at the Little Falls of Elk River. The same gentleman also 
described to me a mineral which he had seen, brought from Swan River, supposed 
to be copper, or some more valuable metal; but I think there is little doubt, from 
the appearance and character of the ore as described to me, that it was only iron 
pyrites. 
The rocks of this locality are of a character such as have yielded valuable ores 
in some regions of the old world, but their elevation is but little above high water ; 
and, except over limited tracts, they are entirely hidden from view by deep depo- 
sits of drift. This circumstance renders them inaccessible, except at great expense, 
and indicates no important axes of upheaval, favourable for mining operations. 
Seven to eight miles above Osakis Rapids, a short distance below Little Rock, is 
a higher exposure of crystalline rocks. A ridge of hornblende and syenitic green- 
stone, with veins of granite, bearing north 70° to 80° east, rises on the east side of the 
Mississippi to the height of thirty to forty feet; and, a short distance further back, 
even to the height of sixty to seventy feet. This is, according to our observations, 
in latitude 45° 39’ 34”, and just opposite to a very extensive plain on the west side 
of the Mississippi, in the new Winnebago purchase. This plain presented, at the time 
we visited it, a most animated appearance: several hundred Winnebago Indians 
were encamped on it, having lately arrived from their former home in Iowa, pre- 
paratory to spreading themselves over their new hunting-grounds. 
About a mile and a half above Little Rock, a tough, close-grained hornblende 
rock appears on both sides of the Mississippi, in situ, elevated from two to four feet 
above the water-level, and overlaid by sand and gravel. Similar rocks appear at 
intervals between Little Rock and Knife Rapids. 
From the occurrence of superficial, ferruginous crusts, in the pools of water col- 
lected in the hollows of these rocks, it is evident that oxide of iron enters largely 
into their composition, and exists in a state easily acted upon by the water. 
Five or six miles above the mouth of Swan River,* on the Mississippi, is an in- 
teresting exposure of gray-coloured mica-slate, charged with large crystals of stau- 
rotide. The surfaces of the crystals are, however, rather rough, which impairs 
their beauty as cabinet specimens. This rock is exposed at intervals for three or 
four miles. 
This mica-slate is succeeded, yet higher up on the Mississippi, by magnesian 
slates, associated with a tough, close-grained, hornblendic rock. The best exposure 
of these, is on the rapids, four miles above the mouth of Elk River of Nicollet, where 
they have a bearing of north 20° east, and lie either nearly vertical, or with a dip 
of 75° to 80° to the southeast. The slate has quartz veins running through it; 
there is, however, but little opportunity to investigate its mineral character, for the 
* This river is about three miles above our encampment of the night of the 11th of September, at 
which place two observations were taken, one of Altair and one of Polaris, which gave for the latitude, 
45° 48" 49": 
