Squder—Peculiar Deposits on the Mississippi Bluffs. 269 
exposure of rock in place was observed anywhere about them* 
Whatever rock cores there may be in these ridges, they are 
deeply covered by rock waste from the lower Magnesian. The 
drainage passes through the ridge by a notch barely wide 
enough at bottom for the torrent course and very steep. 
Both in its bed, and in the ends of the ridges, there is nothing 
visible save the limestone debris of which the fragments 
are unusually large, and from the notch to the foot of the 
bluff the torrent course is a continuous cascade over similar 
material. One can hardly overlook the strong morainic aspect 
of these ridges in their entirety, yet they are so very massive, 
and prominent that I hesitate to claim them as such until 
further evidence is available. 
I have shown that even where a bluff is being most rapidly 
removed by erosion, the talus shows no tendency to survive the 
disappearance of its parent ledge. The occurrence now to be 
described will show how extreme an endurance would under 
the hypothesis have to be assigned to it. 
At the head of one of the small valleys in the Trempealeau 
bluffs is a col whose lowest point is somewhat above the base, 
of the Madison sandstone. Along the south side of this col 
for a distance of 350 feet the deposits occur, partly reaching 
the summit and partly falling short of it, also showing lobate- 
extensions down the hillside seventy-five feet or more below 
the main body. The col separates two opposing valleys, that 
on the north being much the shorter. While the river occupied' 
its northern channel it would have had the advantage of the- 
steeper gradient. Since that time there has been little advan¬ 
tage either Way. 
In Fig. 2, I show a section of the hill as it now exists, in 
solid lines, and on the north side, in broken lines, a section of 
the hill as it must have existed in order to have furnished the 
material, and indicating what must have been removed since 
the deposits were formed, the deposits and the south side of 
the hill meanwhile remaining intact. It amounted to a south¬ 
ward migration of the divide of about 150 feet. 
In the occurrences thus far described there has been nothing 
19—S. & A. 
