Subsequent geological agencies have greatly modified the primary result. The ocean has been permitted still again to sweep over the continent, and the crests of the folds and ridges have all been planed down, and the materials distributed over the intervening spaces, or worked up in the rock-building of later ages. Thus the original height of the Alleghanies has been much reduced. Thus the swell upon which the Queen City of the West is built has been worn off to the level of the adjacent areas; and thus the original limits of the great Carboniferous jungle have been very much restricted.

feet in height, and extending from New England to Alabama. Some of the folds of the Appalachian upheaval, according to the grand generalizations of the brothers Rogers, were protruded with so abrupt a flexure, and to such a dizzy height, that they toppled over toward the west; while to the west of the principal axis of violence the folds become gentler, and terminate in pleasant undulations of the surface. The Queen City of the West stands, perhaps, on the last of this series of undulations. Thus were the Appalachians brought into existence. Thus were the deep-seated beds of coal lifted above the general level of the land, and brought within the reach of moderate excavations, accompanied by the requisite conditions for nat

ural drainage of the mines (Fig. 68).

Fig. 68. The North American Continent at the end of Paleozoic Time, or begin

ning of Mesozoic.

lines the rivers.)

(The dotted lines represent its present outlines; the broken

Subsequent geological agencies have greatly modified the primary result. The ocean has been permitted still again to sweep over the continent, and the crests of the folds and ridges have all been planed down, and the materials distributed over the intervening spaces, or worked up in the rock-building of later ages. Thus the original height of the Alleghanies has been much reduced. Thus the swell upon which the Queen City of the West is built has been worn off to the level of the adjacent areas; and thus the original limits of the great Carboniferous jungle have been very much restricted.

feet in height, and extending from New England to Alabama. Some of the folds of the Appalachian upheaval, according to the grand generalizations of the brothers Rogers, were protruded with so abrupt a flexure, and to such a dizzy height, that they toppled over toward the west; while to the west of the principal axis of violence the folds become gentler, and terminate in pleasant undulations of the surface. The Queen City of the West stands, perhaps, on the last of this series of undulations. Thus were the Appalachians brought into existence. Thus were the deep-seated beds of coal lifted above the general level of the land, and brought within the reach of moderate excavations, accompanied by the requisite conditions for natural drainage of the mines (Fig. 68).

Fig. 68. The North American Continent at the end of Paleozoic Time, or beginning of Mesozoic. (The dotted lines represent its present outlines; the broken lines the rivers.)

Subsequent geological agencies have greatly modified the primary result. The ocean has been permitted still again to sweep over the continent, and the crests of the folds and ridges have all been planed down, and the materials distributed over the intervening spaces, or worked up in the rock-building of later ages. Thus the original height of the Alleghanies has been much reduced. Thus the swell upon which the Queen City of the West is built has been worn off to the level of the adjacent areas; and thus the original limits of the great Carboniferous jungle have been very much restricted.