196 Cincinnati Society of Natural History. 
posed of fragments of the rocks in situ, showing that, whatever may 
have been its origin, it could not have been acted upon by long con- 
tinued agencies. A few foreign pebbles exist in it, generally trap, and 
evidently derived from the neighborhood. Greatest thickness 30 feet. 
2d. Drift clay, or red clay. It is a mixture of loam and clay, and. 
its color is owing to the decomposition of the red sandstone and trap 
from which it has been derived. It is mainly composed of very finely 
comminuted substances, yet there are pebbles interpersed through it,and 
even bowlders of considerable size, generally rounded and smoothed. 
Fragments of metallic ores and native copper occur occasionally in it— 
the latter sometimes weighing several hundred pounds. It is found 
along the whole southern coast of lake Superior, resting upon the red 
sandstone, and limited to a certain height, but on the Ontonagon and 
Carp rivers, it is found in depressions on elevated lands, 500 feet above 
the lake. At Grand Sable where its base rests on almost horizontal 
strata of red sandstone, a few feet above the water, and its top is 
covered by a mass of drift sand, it is 60 feet in thickness, and ex- 
hibits lines of stratification disposed with great regularity. 
3d. Drift sand and gravel. This is the most widely diffused of the 
drift deposits on the shores of lake Superior and the northern part of 
Michigan. The greatest thickness observed is at Grand Sable, where 
it is 300 feet thick. 
4th. Bowlders. These occur of every size and description in great 
numbers along the whole southern shore. The largest noticed being 
of hornblende, and measuring 15 feet in length, 11 in width, and 64 in 
height. The bowlders have been moved from north to south, but have 
not come from far, though some of them have been transported from 
the north shore. It is noticed among the ridges north of Carp river, 
that the valleys, for the most part, contain bowlders from the next 
ridge to the north; and there are instances where a ridge did not allow 
the fragments of the preceding ridge to pass. This limitation pre- 
vails only within the hilly portion of the Lake Superior region between 
the lake shore and the dividing ridge. South of thisridge no barrier 
occurs. 
5th. Drift terraces and ridges. These may be seen both on the 
north and the south sides of Lake Superior, but they are less striking 
than around Lakes Erie and Ontario. They are most conspicuous on 
the south shore, between Saut and Keweenaw point. Their average 
height is about 100 feet. At a place two miles east of Two-hearted 
river, the following succession occurs: gravel beach, 5 feet ; sand 
