=The Atlantic Slope.=--The Atlantic slope of the United States is described in the New Jersey State Geological Survey's report on the Physical Geography of the State as "a fairly distinct geographical province. Its eastern boundary is the sea; its western boundary on the north is the divide between the drainage flowing southeast to the sea and that flowing northeast to the St. Lawrence. Farther south its western limit is the divide between the streams flowing east to the Atlantic and those flowing west to the Ohio and Mississippi Rivers." The line between it and the geographical province next west follows the watershed of the Appalachian system of mountains. It is divided, according to elevations, into several subprovinces, all of which elongate in a direction roughly parallel to the shore. Next to the coast there is usually a belt of lowland, few or many miles wide, called the _Coastal Plain_. Inland from the Coastal Plain is an intermediate height, between the Coastal Plain to the east and the mountains to the west, known in the South as the _Piedmont Plateau_. The mountainous part of the slope constitutes the third province, known as the _Appalachian Zone_. The Atlantic slope may be divided into two sections--a northern and a southern--in which the Coastal Plain is narrow and wide respectively. These two sections meet in New Jersey, where the division runs from the Raritan River, just below New Brunswick, to Trenton. South of this line the Coastal Plain expands, and all considerable elevations recede correspondingly from the shore. These three subprovinces are especially well shown in the southern section of the Atlantic slope. They are less well developed in the northern section, and even where the topography is comparable the underlying rock structure is different. In New Jersey a fourth belt, the Triassic formation, is interposed between the Coastal Plain and the Highlands corresponding to the Piedmont Plateau. North of New Jersey the Coastal Plain has little development, though Long Island and some small areas farther east and northeast are to be looked upon as parts of it.