It is natural in so great a variety of climate that there should be a corresponding difference in the produce of the soil; that one part should raise what the other might want.  It is equally natural that the pursuits of industry should vary in like manner; that labor should be cheaper and manufactures succeed better in one part than in another; that were the climate the most severe and the soil less productive, navigation, the fisheries, and commerce should be most relied on.  Hence the motive for an exchange for mutual accommodation and active intercourse between them.  Each part would thus find for the surplus of its labor, in whatever article it consisted, an extensive market at home, which would be the most profitable because free from duty.

There is another view in which these improvements are of still more vital importance.  The effect which they would have on the bond of union itself affords an inducement for them more powerful than any which have been urged or than all of them united.  The only danger to which our system is exposed arises from its expansion over a vast territory.  Our union is not held together by standing armies or by any ties other than the positive interests and powerful attractions of its parts toward each other.  Ambitious men may hereafter grow up among us who may promise to themselves advancement from a change, and by practicing upon the sectional interests, feelings, and prejudices endeavor under various pretexts to promote it.  The history of the world is replete with examples of this kind—­of military commanders and demagogues becoming usurpers and tyrants, and of their fellow-citizens becoming their instruments and slaves.  I have little fear of this danger, knowing well how strong the bond which holds us together is and who the people are who are thus held together; but still, it is proper to look at and to provide against it, and it is not within the compass of human wisdom to make a more effectual provision than would be made by the proposed improvements.  With their aid and the intercourse which would grow out of them the parts would soon become so compacted and bound together that nothing could break it.

The expansion of our Union over a vast territory can not operate unfavorably to the States individually.  On the contrary, it is believed that the greater the expansion within practicable limits—­and it is not easy to say what are not so—­the greater the advantage which the States individually will derive from it.  With governments separate, vigorous, and efficient for all local purposes, their distance from each other can have no injurious effect upon their respective interests.  It has already been shown that in some important circumstances, especially with the aid of these improvements, they must derive great advantage from that cause alone—­that is, from their distance from each other.  In every other way the expansion of our system must operate favorably for every State in proportion as it operates