Southern Spain, resembles Morocco, more than Navarre; Provence, resembles Algeria, rather than Dauphiny; Senegambia, the Amazon, rather than the Red Sea; and the great valley of the Amazon, is more like to the moist regions of Africa than it is to its arid neighbors, Peru, Chili, &c. The symmetry of the Atlantic is still more striking in its under-currents and the winds and breezes that sweep over it. Their action potently helps to create these analogies, and to form what we may call the _fraternity of the shores_. The principle of Geographical unity, will be more and more sought for in the _maritime basin_, where the waters and the winds, faithful intermediaries, create the relation, the assimilation, of the opposite shores. Far less can we ask this illustration of Geographical unity from the mountains, where two slopes frequently present to you, under the same latitude, both a Flora and a population absolutely different; on the one slope, eternal summer, on the other, eternal winter, according to the aspect of each. The mountain rarely gives unity of country; far more frequently, duality, discordance, actual diversity. This striking state of the case was first pointed out by Borg. de Saint Vincent, and has since, in a thousand instances, been confirmed by the discoveries of Maury. In the immense valley of the sea, beneath the double mountain of the two continents, there are, strictly speaking, only two basins:-- 1. _The basin of the Atlantic_; 2. _The great basin of the Indian Ocean, and the Pacific._ We cannot give the name of basin to the indeterminate cincture of the great Austral Ocean, which has no boundary save that on the north it is touched by the Indian Ocean, the Coraline and the Pacific. The Austral Ocean alone exceeds in extent all other seas together, and covers almost one-half of the entire globe. Apparently, the depth of that sea is in proportion to its extent. While recent soundings of the Atlantic give a result of 10,000 to 12,000 feet, Ross and Denham found in the Southern Ocean from 14,000 to 46,000 feet. Here, too, we may note the mass of the Antarctic ice, infinitely more vast than the Arctic. We shall not be very wide of the truth, if we say that the southern hemisphere is the world of waters, the northern the world of land.