While mountains and mountain chains all over the world, and low lands, also, have undergone uplifts, in the course of their long history, that are not explained on the idea that all mountain elevating is simply what may come from plication or crushing, the component parts of mountain chains, or those simple mountain or mountain ranges that are the product of one process of making – may have received, at the time of their original making, no elevation beyond that resulting from plication.

This leads us to a grand distinction in orography, hitherto neglected, which is fundamental and of the highest interest in dynamical geology; a distinction between –

1. A simple or individual mountain mass or range, which is the result of one process of making, like an individual in any process of evolution, and which may be distinguished as a monogenetic range, being one in genesis; and

2. A composite or polygenetic range or chain, made up of two or more monogenetic ranges combined.

The Appalachian chain – the mountain region along the Atlantic border of North America – is a polygenetic chain; it consists, like the Rocky and other mountain chains, of several monogenetic ranges, the more important of which are: 1. The Highland range (including the Blue Ridge or parts of it, and the Adirondacks also, if these belong to the same process of making) pre-Silurian in formation; 2. The Green Mountain range, in western New England and eastern New York, completed essentially after the Lower Silurian era or during its closing period; 3. The Alleghany range, extending from southern New York southwestward to Alabama, and completed immediately after the Carboniferous age.