Mr. Jefferson, by the acquisition of Louisiana and the extension of our Southern limits, therefore, “saved” the Northwest from a negro population and so-called slavery, just as the acquisition of Texas by President Tyler and the eminent and far-seeing Calhoun and others, at a later day, opened other and still wider regions adapted to the wants and specific nature of our negro population, and which are now, by the natural and indestructible laws of climate and industrial adaptation, gradually withdrawing this population from the border or transition States. Indeed, one only needs to examine the several census returns of the federal government, from 1790 to 1860, to understand both the history of the country, in these respects, and the operation of the laws of climate and industrial adaptation. They will then see that the negro element constantly tends southward—a black column ever on the march for its own centre of existence—an advance guard of American civilization, that moves on without cessation, and that must continue to advance until it is in perfect accord with those external conditions to which it is naturally adapted. Nor is the interest of the master—the increased value of the negro labor—the sole motive power, though certainly the leading cause of this progress southward. The increased and increasing white population, with the vast European emigration, is pressing on its rear, while the demands of modern society for the products of its labor, and many other influences, are every day increasing in force, and impelling the negro tropic-ward with greater rapidity at present, perhaps, than ever before.