It will readily be perceived that since industrial and commercial development is necessitating dependence and unity, it is equally true that the natural varieties of soil and climate are, also, conditions of like dependence and unity. When these diversities of soil in different sections are fully developed, and the exchange of products readily made through improved commercial facilities, and human wants multiplied by means of civilized culture, agricultural specialization creates the demand, not for political division and isolation, but for more extensive organization. That New England manufactures is no reason that she should separate her government from that of the other States, but just the reverse. That the Middle States are more distinctively a mining region, and the great West agricultural, is no reason that their general government should be distinct, but precisely the reverse. That the South produces cotton, rice, and sugar, is no reason for her seceding from the Union, but exactly the reverse. These diversified interests, we repeat, create interrelation and dependence, unitizing the commercial and industrial polity; and the political organization should, as far as possible, be coextensive therewith. There are physical necessities which prevent the formation and maintenance of a comprehensive political organization in the earlier stages of civilization, but these never have obtained in the United States, and every hour's improvement carries us farther beyond them. All the results of a progressive civilization are constantly complicating the dependence and interrelation of various sections of our country. Roads, railroads, canals, and lines of telegraph, by their connections and intersections, are so many bonds of union between the various districts of our country--so many bonds of union between the various States of the confederacy--and forbid its dissolution. Even Nature conspires with civilization to the same end. The great valleys and rivers running north and south are so many natural ties, which the most incorrigible perverseness, on the part of man, could alone prevent from performing the office to which they seem so happily adapted in the play of the civilized elements. As we have seen in our brief view of Europe, greater political unitization has been the result of growth in civilization. In the United States, all natural, commercial, and industrial bonds of union are becoming more fully developed. This evinces the direction of progress.