44 PROTOZOIC ROCKS. 
the strata, by which the beds that have been rising, as one ascends the streams, dip 
again, descending towards the river beds. While this local dip of the strata con- 
tinues to prevail, the beds, which had nearly run out, again thicken, and constitute, 
as before, the principal part of the hills. Thus, though opposite Winnesheik’s 
Village, and below the mouth of Bad Axe River, the Lower Magnesian Limestone 
capping the bluffs, is only from one hundred and thirty to one hundred and fifty 
feet thick, it again increases, five miles higher up, to one hundred and seventy-five 
feet.* Between this and Prairie 4 la Crosse, the northerly rise again sets in, so 
that at Mountain Island, the sandstone constitutes the great body of the hill, to the 
height of four hundred and twenty-eight feet.+ About this part of the Mississippi, 
we have, in fact, what, in the language of the geologist, is termed the principal axis 
of the protozoic strata of the Upper Mississippi; or the geological backbone, whence 
the strata again decline, with local undulations, towards the Falls of St. Anthony. 
Pine bpm Moony ” oe asi 
cis. Ra ae. 
OUTLET OF LAKE PEPIN. 
Below the outlet of Lake Pepin, the Lower Sandstone constitutes about three 
hundred and twenty to three hundred and forty feet of the base of the hills,{ while, 
above this, the Lower Magnesian Limestone rises one hundred and sixty feet. At 
the great bend of that lake, on the northeast side, the Lower Magnesian Limestone 
may be seen, forming a perpendicular wall, of nearly two hundred feet; the total 
height above the lake being about four hundred feet.¢ This conspicuous escarp- 
ment is the spot celebrated in Indian annals as the Maiden’s Rock,|| or Cap des 
Sioux ; represented on the opposite page. 
Lake Pepin is a mere expansion of the channel of the Mississippi, produced, ina 
great measure, by the eroding and undermining action of its waters, combined with 
atmospheric agencies, scooping out and carrying away the inferior soft sandstones. 
. 
* See Sect. 1, B and C. T See Sect. 1, No. 7, D and E. 
} See Sect. 1, I. § See Sect. 1, K. 
|| The romantic legend connected with this conspicuous point, is related in Long’s Expedition. It is 
sometimes called the Lover’s Leap. 
