The rugged region embracing the Adirondacks, together with the more elevated portions of New England and of the adjacent provinces of Canada, has many geographical features that are similar to those of the southern Appalachians, but at the same time this, the central portion, differs in a marked way from the southern extension of the Atlantic mountains. The higher mountains in each of these picturesque regions are at least in a general way to be considered as the unconsumed remnants of ancient uplands, the greater part of which have been eroded away. The most marked contrast in the scenery of these two regions of similar elevation is due to the presence of a great number of lakes at the north, many of them of large size, and the total absence of such beautifying elements in the landscapes at the south. The streams at the north are frequently impetuous and broken by many cataracts and rapids, thus furnishing abundant water-power; while at the south the streams flow through more evenly graded channels and are without cascades except near their sources in the mountains. These contrasts are such as are to be found the world over between regions of young and old topography. The differences in the degree of development reached by the streams of the New England region as contrasted with those of the southern Appalachians, finds an explanation in the fact that New England, Canada, etc., was formerly covered with glacial ice, and on the retreat of the glaciers the surface of the land was left with an essentially new relief, while the southern Appalachians were well to the south of the great ice invasion, and the streams of that region have reached a mature development, except near the sources of their head-water branches, which, like the topmost twigs of a tree, are always young.