through regular changes toward a well-defined end, the continents have grown steadily and consistently from the beginning, through successive accessions in a definite direction, to their present form and Organic correlations.  If, indeed, there is any meaning in the remarkably symmetrical combinations of the double twin continents in the Eastern Hemisphere, so closely soldered in their northern half, as contrasted with the single pair in the Western Hemisphere, isolated in their position, but so strikingly similar in their Outlines, they must be the result of a progressive and predetermined growth already hinted at in the relative position and gradual increase of the first lands raised above the level of the ocean.

However this may be, there can be no doubt that we now know with tolerable accuracy the limits of the land raised above the water at that period in the present United States.  Let us see, then, what we inclose between oar two lines.  We have Newfoundland and Nova Scotia, the greater part of New England, the whole of New York, a narrow strip along the north of Ohio, a great part of Indiana and Illinois, and nearly the whole of Michigan and Wisconsin.

Within this region lie all the Great Lakes.  The origin of these large troughs, holding such immense sheets of fresh water, remains still the subject of discussion and investigation among geologists.  It has been supposed that in the primitive configuration of the globe, when the formation of those depressions at the poles in which the Arctic seas are accumulated gave rise to a corresponding protrusion at the equator, the curve thus produced throughout the North Temperate Zone may have forced up the Canada granite, and have caused, at the same time, those rents in the earth’s surface now filled by the Canada lakes; and this view is sustained by the fact that there is a belt of lakes, among which, however, the Canada lakes are far the largest, all around the world in that latitude.  The geological phenomena connected with all these lakes have not, however, been investigated with sufficient accuracy and detail, nor has there been any comparison of them extensive and comprehensive enough to justify the adoption of any theory respecting their origin.  In an excursion to Lake Superior, some years since, I satisfied myself that the position and outline of that particular lake had their immediate cause in several distinct systems of dikes which intersect its northern shore, and have probably cut up the whole tract of rock over the space now filled by that wonderful sheet of fresh water in such a way as to destroy its continuity, to produce depressions, and gradually create the excavation which now forms the basin of the lake.  How far the same causes have been effectual in producing the other large lakes I am unable to say, never having had the opportunity of studying their formation with the same care.