1895] MARYLAND ACADEMY OF SCIENCES. 243 
Pennsylvania and Delaware, and it is separated from Virginia 
by a line drawn from the Atlantic Ocean to the western bank 
of the Potomac River and low water line on the Virginia shore, 
this being the southern border of Maryland from the source 
down. From the source of the Potomac a line runs north to 
Mason and Dixon’s line. The gross area of the state is 12,210 
square miles: 9680 land; 1203, the Maryland part of the 
Chesapeake ; 93, Assateague Bay ; and 1054, smaller estuaries 
and rivers. 
The three leading topographical regions of the eastern por- 
tion of the United States, viz., the Coastal Plain, the Pied- 
mont Plateau, and the Apalachian region are all typically 
represented within the limits of the state. The Coastal Plain, 
or tide-water Maryland, forms the eastern portion, lying south 
of aline drawn from Wilmington to Washington, through 
Baltimore. This is closely outlined by the track of the Penn- 
sylvania Railroad; it covers about 5000 square miles. The 
Eastern Shore, except in the extreme north, does not reach at 
any point 100 feet in elevation, while most of it is below 25 
feet. It is deeply cut up by tide-water rivers and bays. This 
also describes the tract known as the “Necks” between Balti- 
more and Havre de Grace. The temperature is much modified 
by the surrounding water, the southern portion having a mean 
annual temperature of 58°; but the greater part lies between 
56° and 54°; the northern part averaging 52°. Southern 
Maryland or the Western Shore is different, considerable of it 
reaches 100 feet, and in places as much as 180 feet. The mean 
annual temperature seldom exceeds that of Baltimore, which is 
55.6°, by more than 2°, 
The Piedmont Plateau, or Central Maryland, extends from 
the Coastal Plain to the Catoctin Mountain, and has an area of 
about 2500 square miles; it is broken by low, undulating hills, 
which gradually increase in elevation to the westward. Along 
the eastern margin, heights exceeding 400 feet are frequently 
reached, and at Catonsville 525 feet, while at Parr’s Ridge, in 
Carroll County, it rises above 850 feet, At Frederick City, 
