SURFACE GEOLOGY. 3 
scratches have very different bearings, conforming in a rude way to the 
present topography, and following the directions of the great lines of 
drainage. In Canada, and in our Hastern and Middle States, these ice- 
marks are universal. In the Mississippi valley, on certain uplands, like 
those of the Wisconsin lead-region, no glacial furrows have been discov- 
ered; but on most of the highlands, and in all the lowlands, lake-basins, 
and great valleys, they are distinctly discernible down to the limits 
specified, if the underlying rock has been such as to retain them. 
2d. Some of the valleys and channels which bear the marks of glacial 
action—evidently formed by ice, and dating from the ice period, or an 
earlier epoch—are excavated far below the present lakes and water- 
courses which occupy them. These valleys seem to form connected lines 
of drainage at a lower level than the present river systems, and in part 
lower than the present sea level; such, indeed, as could not now be pro- 
duced without a continental elevation of several hundred feet. The evi- 
dence on which this assertion is based will be cited farther on. 
3d. Upon the glaciated surface we find a series of unconsolidated 
materials, generally stratified, called Drift deposits. Of these, the first 
and lowest, though not always present, is a tough, blue, unstratified 
clay, generally thickly set with small stones; more rarely containing 
those of larger size, ground and scratched. From this character it is 
called the bowlder clay. In the Hastern States, and near outcrops of 
crystalline rocks, sheets or heaps of gravel and bowlders are @ meqimeniuly 
found resting upon the glaciated surface. 
4th. In certain localities the pebbly “‘hard-pan,” or bowlder clay, is 
overlaid by a greater or less thickness of fine, laminated clay, without 
pebbles. This laminated clay corresponds closely with the ‘“‘ Saugeen 
clay ” of Sir William Logan, but it shades into the bowlder clay below 
in such a way that it is impossible to draw any distinctly marked line 
between them. Both the laminated and pebbly clays are, therefore, re. 
garded as parts of one formation, and the name Krve clay is retained 
for that, since it was coined by Sir William, Logan to designate its 
exact equivalent on the north shore of Lake Erie. 
Sth. On the surface of the clays I have mentioned there is umd over 
a large area in Ohio and other Western States, a layer of carbonaceous 
matter, with logs and stumps, and sometimes upright trees. This car- 
bonaceous layer I have termed the Forest Bed, since it is apparently an 
ancient soil which sustained a growth of vegetation that covered a large 
part of the area previously occupied by the ice-sheet. In some parts of 
southern Ohio this horizon is marked by deposits of peat now deeply 
buried under the later-formed deposits of the Drift. The remains of the 
