2. Unity. Between the Rocky Mountains and the Atlantic coast, and between the Gulf of Mexico and the northern wheat-limit, a larger space of fertile territory, embracing a wider variety of climate and production, is thrown into one mass, broken by no barrier, than can, perhaps, elsewhere be found. 3. Communication. No mass of land equal in other advantages is to the same extent thrown open and enriched by natural highways. The first item under this head is access to the ocean, which is the great road-space and highway of the world. Not mentioning the Pacific, as that coast is not here considered, we have the open sea upon two sides, while upon the northern boundary is an inclosed sea, the string of lakes, occupying a space larger than Great Britain and Ireland, and of a form to afford the greatest amount of coast-line and accommodation in proportion to space. But coast-_line_ is not enough; land and sea must be wedded as well as approximated. The Doge of Venice went annually forth to wed the Adriatic in behalf of its queen, and to cast into its bosom the symbolic ring; but Nature alone can really join the hands of ocean and main. By bays, estuaries, ports, spaces of sea lovingly inclosed by arms of sheltering shore, are conversation and union established between them. "The sea doth wash out all the ills of life," sings Euripides; and it is, indeed, with some penetration of wonder that one observes how deep and productive a relation to man the ocean has sustained. Some share in the greatest enterprises, in the finest results, it seldom fails to have. Not capriciously did the subtile Greek imagination derive the birth of Venus from the foam of the sea; for social love,--that vast reticulation of wedlock which society is--has commonly arisen not far from the ocean-shore. The Persian is the only superior civilization, now occurring to our recollection, which has no intimate relation either with river or sea; and that pushed inevitably toward the Tigris and Euphrates. Now to Europe must be conceded the supremacy in this single respect, that of representing the most intimate coast relation with the sea; North America follows next in order. Africa, washed, but not wedded, by the wave, represents the greatest seclusion,--and has gone into a sable suit in her sorrow. After the ocean, rivers, which are interior highways, claim regard. The United States have on this side the Rocky Mountains more than forty thousand miles of river-flow, that is, eighty thousand miles of river-bank,--counting no stream of less than one hundred miles in length. Europe, in a larger space, has but seventeen thousand miles. The American rivers are nearly all accessible from the ocean, and, owing to the gentle elevation of the continent, flow at easy declivities, and accordingly are largely navigable. The Mississippi descends at an average of only eight inches _per_ mile from source to mouth; the Missouri is said to be navigable