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 Avith 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". 



