184 The American Geologist. March, i9uo 
divides may owe their unsymmetrical positions to the drowning, and 
hence shortening, of the lower courses of the streams. 
The author finds that during historic time alterations have taken 
place in the streams and coast lines. The geological and physical 
features of the coastal plain are found to have largely determined the 
pursuits of its inhabitants: — peach farms are located along the parallel 
belts of sandy loam of Cretaceous and Eocene age; wheat, grass and 
tobacco, upon the Miocene clays; berries and melons upon the lighter 
sandy loams of the Pliocene and Pleistocene; the drowned streams and 
coastal lagoons form admirable localities for oyster beds. 
The Piedmont region of Maryland is a gently rolling plateau whose 
surface, traversed from northeast to southwest by Parr's ridge, slopes 
gently eastward and westward. It differs from the coastal plain in 
that its forms appear not to be related to structure. The author dis- 
cusses this region in three sections: — The upland, the valleys in the 
upland, and the residual masses above the upland. The most striking 
feature of Piedmont topography is the even skyline of its hills. The 
divides have flat, convex curves at the points farthest from the present 
channels, but in the valleys the gentle arches change to equally gentle 
concavities, interrupted by gorges. The restored surface would not 
be perfectly even, but would show low hills and broad valleys, similar 
to those which may now be seen in some undrained areas along Parr's 
ridge.' The surface thus restored, which is known as the Schooley 
peneplain, occupies a tilted position, rising from four hundred feet at 
the fall line to nine hundred at Parr's ridge. The Schooley peneplain 
bevels strata of all ages from Archean to Jurassic, the present Pied- 
mont upland representing the denuded remnant of the former Pied- 
mont mountain chain. The Schooley peneplain was probably pro- 
duced during Triassic and Jurassic times, since it bevels Jurassic stra'.a 
while above its surface Potomac deposits are found. 
The valleys in the upland are found to be of three types. One class 
has the steep sides and narrow channels characteristic of young 
streams; another has the gently sloping convex sides characteristic of 
the Schooley peneplain; the third possesses broad benches at several 
levels. Dr. Abbe considers numerous streams in detail and finds that 
the majority belong to the first class near mouths while their upper 
courses are of^the second class. In general the young portions are not 
related to structure, while the mature portions follow the lines of 
less resistant rocks. The age of the mature valleys is indicated by 
the presence of occasional masses of sand and gravel. The oldest of 
these deposits is of late Potomac age; the peneplain was completed in 
early Potomac time; hence the valleys must have been produced dur- 
ing the Middle Potomac. These two classes of streams belong to 
the eastern side of the Piedmont region; the third class, consisting only 
of the Monocacy and its tributaries, flows westward from Parr's ridge. 
On the lowlands of the Newark formation this river has carved out its 
channel, three terraces indicating its history. Above the general sur- 
