Squier-—Peculiar Deposits on the Mississippi Bluffs. 267 
Prom this knob like end, the low ridge—the form the deposit as¬ 
sumes—follows down the crest of the bluff, which in the Men- 
dota horizon still presents a partly mural front to the river. 
Then curving it follows a course more directly down the hill¬ 
side nearly to the bottom. (In one of the three examples in 
this class it crosses the valley bottom and runs up an unascer¬ 
tained distance on the other side of the valley, and is partly 
cut through by the drainage channel.) 
It is apparent therefore that even under the most favor¬ 
able conditions the talus shows not the slightest tendency to 
superior endurance, while the deposits in question show char¬ 
acteristics, and extend to points for which the hypothesis offers 
no explanation. Occurrences to be described, will show both 
how great an antiquity the hypothesis would require that we 
assign the deposits, also that in fact they are quite recent. 
The topographic features to which I have applied the 
term circs, are the joint product of the active erosion induced 
by the near vicinity of the river, and of the rather definite 
composition, and arrangement of the stratigraphic pile on 
which it acts. 
They are therefore not only limited to the near vicinity of 
the river, but also to a rather short stretch of the river, about 
forty miles in length. The dip of the strata, both up and 
down the river bringing about an entire change in the 
character of the stratigraphic pile, and a corresponding change 
in the erosional forms. The circs show narrow outlets, floors 
of moderate slope which widen rapidly upward, ending in wide, 
but steep, sometimes precipitous, slopes next the bluffs. The 
buttresses naturally reverse the conditions, being narrow next 
the bluff, and widening rapidly outward. Plate XIV, Fig. 2, 
which is a view looking along the south front of the main maso 
of the Trempealeau Bluffs, shows a good example of this topo¬ 
graphic type, two circs with their separating buttress, being 
seen in the foreground. 
The deposits are found on the buttress in the foreground, on 
the further side of the second circ, and on the hither edge of 
a circ in the background, also on a buttress still further along, 
