There can be no doubt that the varieties of climate and the peculiarities of countries, as it regards their animal and vegetable productions, are dependent on the same causes. The distribution of species has been referred by some to specific centres of creation around which the plants and animals have spread, without reference to physical conditions. Although centres of creation may be admitted, these centres themselves have been determined by the physical fitness of each centre to the conditions of the creation, and in like manner the migration of tribes is solely due to these physical forces we have been considering. In every zone we find that vegetable organization is peculiarly fitted for the considerations by which it is surrounded. Under the equator we have the spice-bearing trees, the nutmeg, the clove, the cinnamon, and the pepper-tree; there we have also the odoriferous sandal, the ebony, the banyan, and the teak: we have frankincense, and myrrh, and other incense-bearing plants; the coffee-tree, the tea-plant, and the tamarind. A little further north we have the apricot, the citron, the peach, and the walnut. In Spain, Sicily, and Italy, we have the orange and lemon-tree blooming rich with perfume, and the pomegranate and the myrtle growing wild upon the rocks. Beyond the Alps the vegetation again changes; instead of the cypress, the chesnut, and the cork-tree, which prevail to the south of them, we have the hardier oak, the beech, and the elm. Still further north, we have the Scotch and spruce fir and larch. On the northern shores of the Baltic, and in that line of latitude, the hazel alone appears; and beyond this the hoary alder, the sycamore, and the mountain ash. Within the Arctic circle we find the mezereum, the water-lilies, and the globe-flowers; and, when the weakness of the solar radiations becomes too great even for these, the reindeer moss still lends an aspect of gladness to the otherwise sterile soil. The cultivation of vegetables depends on the temperature of the clime. The vine flourishes where the mean annual temperature ranges between 50° and 73°, and it is only cultivated profitably within 30° S. and 50° N. of the equator. To the same limits is confined the cultivation of maize and of olives. Cotton is grown profitably up to latitude 46° in the Old World, but only up to 40° in the New. We have evidence derived from photographic phenomena, that the constitution of the solar rays varies with the latitude. The effects of the sun’s rays in France and England in producing chemical change are infinitely more decided than, with far greater splendour of light, they are found to be in the lands under or near the equator. Indeed, the remarks made on the variations in the character of the sunbeam with the changing seasons, may apply equally to the variations in latitude.