8 of Witeonsin and part of Fowa, 7 
Ee : ‘the strata cotinar decline ; so that at Red«Rock the fossilifer- 
~ ous ‘shell limestone and. underlying incoherent white siliceous 
~~ eonsin river, and which soon ran out after passing Prairie du | 
Chien, were again in place, forming the table land. Gradually 
‘ increasing in ‘thickness towards St. Paul’s and Carver’s Cave, 
" these beds form there the entire mural ledges above the waters of 
the Mississippi and ee the escarpment of Fort Snelling, 
‘as well as at the Falls of St. Anthony. Five or six miles above: . 
this, these and Mico, all the protozoic strata, are seen for the ‘ 
last time in ascending the Mississippi, being lost under the drift 
- ity of the Sank Rapids where the granite protrudes. 
_ “In regard to’ the physical features of the celebrated country be- 
“tween the mouth of the St. Peter’s and the Falls of St. Anthony, 
_ we extract the following: 
- The Falls of St. Anthony are at present seven miles rane the 
a 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 
5 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 
Bar Mississippi, which forms the base of the falls. 
a. ‘he confused heaps of disjointed masses of limestone, piled 
~~ together below the falls, indicate the undermining action in pro- 
gress. 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 
tari which these es repose, thus “allowin ng them gradually to 
tached and precipitated into the rapids beneath. In this way the 
or, in proportion as the fall shall recede, the sandstone, by rea= 
Son of its dip, will diminish in thickness, and at length disappear 
h the river bed. From observations of the dip at the falls, 
this latter contingency will occur when the fall has been worn 
ck some six or seven miles from its present position 
‘nthony must be more rapid than at the falls of 
since the soft sandstone of the former locality is more cengilee? 
away than the Niagara shale. 
. 
ee ~ sandstone, which crowned the hills bordering on the lower Wis- “+. 
- deposits which cover all the rocky strata from view to the vicin- _ 
, and causing huge blocks to become, from time to time, de- aaa 
fall will, probably, after a lapse of time, be converted into a rapid. — 
here can be little doubt that the rate of erosion at the falls > 
- : 
eo 
ae 
~ 
