Review of Recent Geological Literature. 183 
For historical and stratigraphic reasons, Dr. Abbe considers that it 
should be regarded as extending to the edge of the continental shelf. 
Consequently he describes it as consisting of a submerged and a 
sub-aerial section. These two divisions possess similar broad, even 
surfaces and differ only in that the sub-aerial section is dissected by 
streams. The author finds two types of streams. The' streams of the 
first class antedate the emergence of the coastal plain. They now rise 
in the Piedmont region, flow down the slope of the coastal plain and 
empty into the Atlantic. Formerly they flowed from the Piedmont 
shore into the Mesozoic ocean, and have extended in length with the 
elevation of the coastal plain, always keeping at right angles to the 
shore. The streams of the other and younger class originated on the 
coastal plain itself and are characterized by having winding courses. 
This scheme of drainage is interrupted by Chesapeake bay and the 
areas on either side of this body of water are designated as the eastern 
and western shores of Maryland. The eastern shore has but slight alti- 
tude, its most prominent topographic feature being the broad hight of 
land which forms the divide between the eastward and the westward 
flowing streams. The westward drainage is of two types. Either the 
streams are small, not reaching tide-water, and with broad, shallow, 
alluvium-lined valleys; or they do reach tide water, the lower portion 
of their course being characterized by marshes bounded by steep bluffs. 
The streams of this second type merge into tidal estuaries, their head 
waters belonging to the first type. The streams flowing eastward into 
the Atlantic are small and insignificant in Maryland. They attain a 
greater development in Delaware and in both states belong to the type 
known as "drowned." These streams rise in the region of the swamps* 
which cover the Atlantic-Chesapeake divide. The swamps arose in 
inequalities produced during the Pleistocene submergence, the 
streams having, as yet, had insufficient time to drain them. The divide 
is unsymmetrical in position and the author finds the causes usually 
given for the location of watersheds inadequate as explanations of this 
particular position. 
From the intricate shore lines and "drowned" topography a recent 
depression is to be inferred. The resulting changes in tidal currents 
have brought about the undercutting of certain cliffs and the forma- 
tion of various spits and bars. From these constructive and destruc- 
tive changes McGee concluded that the depression is still taking 
place. Abbe finds that the eastern shore streams are filling up their es- 
tuaries, hence he suggests that the undercutting points to a tilting 
whereby the eastern portion is being raised and the bay portion 
depressed. 
The streams of the western shore present similar characteristics of 
"drowning." These features appear more accentuated than in the 
eastern shore streams, owing to the greater elevation of this section 
at the time of the post-Lafayette emergence. Here also the stream 
divides are unsymmetrical in position. Dr. Abbe suggests that both 
