[Illustration: FIG. 13.--The larger physiographic divisions of North America.] Each of the four physiographic provinces briefly described above is in a conspicuous manner elongated in a north and south direction. The mountains, valleys, and plateaus, as well as the controlling lines of structure in the rocks below the surface, throughout the main body of the continent coincide in direction more or less nearly with the parallels of longitude. At the south, however, and crossing the trend of each of the provinces named above, is the: Fifth, or Caribbean province, which includes the West Indies, the southern part of Mexico, and all of Central America. In this province are the _Antillean Mountains_, now mostly submerged, the principal axes of which trend east and west. With this brief outline of the larger physical divisions of North America in mind, let us endeavour to become acquainted with the leading characteristics of each of the provinces as they exist to-day, and at the same time learn something of their long and varied histories. COASTAL PLAINS AND PLATEAUS _The Coastal Plains._--From New York to Key West and thence about the borders of the Gulf of Mexico to the neighbourhood of Vera Cruz, the border of the present land area of the continent is formed by a low plain, from 30 to 50 miles broad in New Jersey, but increasing in width southward to Georgia and Florida, where its somewhat indefinite inland margin is more than 100 miles from the sea, and reaching its greatest development in the delta of the Mississippi. Extending southward about the west coast of the Gulf, it forms the low, featureless eastern border of Texas, about 50 miles broad, and passes into Mexico, but gradually narrows as the Pacific Mountains approach the coast, and ends in the vicinity of Vera Cruz.