The next contribution to the theory of orogeny was a series of papers published in 1873 by Dana, entitled “On some results of the earth’s contraction from cooling, including a discussion on the origin of mountains and the nature of the earth’s interior.”[88] This contribution, viewed as a whole, ranks among the first half dozen papers on the science of mountains. The following quoted paragraphs give a view of the scope of this article: “_Kinds and Structure of Mountains._” “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 mountains 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. The making of the Alleghany range was carried forward at first through a long-continued subsidence—a _geosynclinal_ (not a _true_ synclinal, since the rocks of the bending crust may have had in them many true or simple synclinals as well as anticlinals), and a consequent accumulation of sediments, which occupied the whole of Paleozoic time; and it was completed, finally, in great breakings, faultings and foldings or plications of the strata, along with other results of disturbance.