THE ATLANTIC LOWLAND. This region, although not large, contains a vast population, and is historically the most important. It made the interior of the continent accessible to dis covery from the east, offered hospitable ground to the colonists, and is rich in the harbors that have led to the building of cities and the growth of commerce, These lowlands are not the same in origin in the North as in the South. The Atlantic rim of New England is a rough lowland rising from sea level to the height of four or five hundred feet. It is beset with rough bills, of native rock, and of glacial waste. It is an uneven but subdued or nearly worn-out mountain country, like western Massachusetts or northern New England, except that it is more fully de graded. South of New York, on the other hand, and reaching to Florida Strait, is the Atlantic Coastal Plain, including southern New Jersey, Delaware, and a broad belt of all the South Atlantic States. It is a smoother land, without projecting masses of rocky hills, and sloping gently up from the tide levels to the rougher lands of the Appalachian belt. It is intersected by Delaware and Chesapeake bays and their rivers, and by more southerly streams. It is often known as the 'tidewater country' be cause the sea enters its estuarine rivers for scores of miles. It is covered with fields of tobacco, cotton, rice, and fruit orchards, or with pastures or native forest. The region is in greater part a sea bottom uncovered at a com paratively recent period, and becomes continuous, beneath the Atlantic waters, with the continental shelf which lies between the land border and the deep seas. West of this plain is a much denuded
belt of ancient Appalachian mountains, which is becoming known as the Piedmont Plain. It is from a few hundred to a thousand feet in alti tude and lies between the coastal plain and the Blue Ridge. See PIEDMONT PLAIN.
One feature of the entire Atlantic coast is that the rivers are tidal. They may occupy nar row- channels to the sea border, like the Hudson, or they may enter at the head of deep and spa cious bays, as do the Delaware and the Sus quehanna. Such a water system with the above rivers, the Potomac, James, and other streams, is well called a 'drowned' river sys tem. By this is meant that the trunk valley and its branches were cut out by land streams, and that the sea has entered their lower harts be cause of a sinking of the edge or of larger parts of the continent. The historical meaning of these conditions can hardly be reckoned. It is enough here to observe that nearly all the harborages and quiet salt waters of our Atlantic border have this origin: and that thins have grown our great seaboard cities, where ships may ride safely at the mouth of tidal streams whose waters offer gateways to the interior of the continent.