200 Cincinnati Society of Natural History. 
having little tenacity, falls in slides and avalanches into the water, and 
is thus cut into deep, narrow gallies by rains. Its surface in the above 
district is not more than 250 feet above the lake, sloping gradually 
from the mountains to the shore, as though it formed, at one time, the 
bed of an ancient sea. On the waters of the St. Louis river on the 
west, and the Ontonagon on the east, however, the red clay deposits 
reach to the height of 450 to 500 feet above the lake. 
On the “ Isle aux Barques” the lime is so abundant in the clay, that 
it has formed in amorphous concretions throughout the mass. A few 
leaves and decayed sticks have been seen in the red marly clays, 
with carbonaceous matter and lignite, but such occurrences are rare. 
Along the coast there are interstratified beds of sand and gravel of a 
local character. In the interior, where the clay is visible in bold 
bluffs, along the water courses, it is more uniform and less inter- 
calated with coarse drift. It rests not only on the sedimentary 
unaltered rocks, but also on trap and metamorphic and igneous rocks. 
The mass of the hills between Chegwomigon bay and the Brule river, 
is gravel and bowlder drift. It is not very uniform in composition, and 
is marked by the violent action of water. The central part of this 
peninsula presents large tracts of barren, water-washed land, and mod- 
erately coarse gravel. Both the western and eastern knobs and ridges 
are of coarse materials; and toward the point or extremity about the 
“detour,” and the adjacent islands, the sand and bowlder deposits are 
represented. 
A section of three miles from the coast to the mountains, four miles 
southwest of La Pointe, showed red marly clay 95 to 130 feet above the 
lake, capped by coarse bowlder drift, the top of which is 428 to 509 
feet above the lake. This drift is disposed in three very abrupt and 
well defined terraces. These terraces continue southward around the 
southern extremity of the mountain, and have the appearance of 
ancient beaches or shores. 
In 1855, Prof. G. C. Swallow* found a fine, pulverulent, absolutely 
stratified mass of light, grayish buff, silicious and slightly indurated 
marl, capping nearly all the bluffs of the Missouri and Mississippi 
within that State, for which he proposed the name Bluff formation. 
The Bluff above St. Joseph exhibits an exposure 140 feet thick. 
It is easily penetrated by the roots of trees, which decay and leave en- 
crusting tubes, giving it a peculiar perfurated appearance. It extends 
from Council Bluffs to St. Louis, and below to the mouth of the Ohio. 
* Geo. Sur. of Missouri. 
