Of the three physiographic provinces into which the Atlantic border region is divisible—the Appalachian district, the Piedmont plateau, and the Coastal plain—the Piedmont plateau preserves the record of the longest and most varied geologic and physiographic history.
The plateau lies at the southeastern foot of the Appalachian system and is separated from the Atlantic ocean by a belt of coastal plain of variable width and from the edge of the continental plateau by a belt of coastal province possessing a uniform width of 200 miles.
The Piedmont district extends north and south from Maine to Alabama, with an average width of 50 miles. Its western limit is defined by the eastern slopes of the Blue ridge; its eastern boundary is defined by an equally conspicuous change in topography, the abrupt transition from a diversified upland to an undiversified lowland.
Eastward from this boundary the . . .