OF THE NORTHWEST. 75 
The Falls of St. Anthony are at present seven miles from the mouth of St. 
Peter’s River. It is, however, more than probable, that they once occupied a 
position at or near Fort Snelling. Of course, little evidence can be gathered of 
the rate of wearing, from actual observation of the inhabitants recently settled 
there, but, judging from the condition of the strata themselves, there must have 
been a rapid retrocession. The cement which holds together the particles of the 
St. Peter’s sandstone is so slight, that it is with difficulty a solid specimen can be 
obtained. Yet this is the rock, with a covering only of fifteen or twenty feet of 
schistose limestone, to protect it from the swift current of the Mississippi, which 
forms the base of the Falls. 
OUTCROP OF UPPER MAGNESIAN LIMESTONE AND SHELL-BEDS, TURKEY RIVER. 
The confused heaps of disjointed masses of limestone, piled together below the 
Falls, indicate the undermining action in progress. The inclined position, too, of 
the ledges of limestone there, for several hundred yards above the chute, contrary 
to the local dip, has mostly been produced by the water which sweeps over them 
entering the extensive rents which run across the strata at this place, and gradually 
washing out the particles of sand upon which these ledges repose, thus allowing 
them gradually to sink, and causing huge blocks to become, from time to time, 
detached and precipitated into the rapids beneath. In this way the fall will, 
probably, after a lapse of time, be converted into a rapid. For, in proportion as 
the fall shall recede, the sandstone, by reason of its dip, will diminish in thickness 
in the gorge, and at length disappear beneath the river bed. From observations 
of the dip at the Falls, this latter contingency will occur when the fall has been 
worn back some six or seven miles from its present position. 
There can be little doubt that the rate of erosion at the Falls of St. Anthony 
must be more rapid than at the Falls of Niagara, since the soft sandstone of the 
former locality is more easily washed away than the Niagara shale. 
On the brink of the gorge, near Fort Snelling, no fluviatile remains have been 
yet found at a height where the waters may be supposed to have flowed in former 
