Of the Catskills, although including only a small portion of the state, there are a number of different topographic features, due to the belts of different rock structure which cross the state from S.W.
A part of the Catskills, and the region farther S., drains into Delaware Bay through the Delaware river.
In the Catskills and in the farming regions the lumber product consists largely of hardwoods (mostly oak, chestnut and hickory), smaller amounts of hemlock and pine, and a very little spruce.
The Catskills are not properly included in the system.
The rivers which most perfectly exemplify this habit are the Delaware, Susquehanna and Potomac; the Hudson, the north-eastern boundary of the middle section, is peculiar in having headwaters in the Adirondacks as well as in the Catskills (northern part of the plateau); the James, forming the south-western boundary of the section, rises in the inner valleys of the stratified belt, instead of in the plateau.