These winds are sometimes drawn aside across the coast line--constituting the Mediterranean sirocco, and the African harmattan. Vessels far off at sea, sailing to the northward, are covered or stained on the weather side of their rigging (that next to the African coast), with a fine light-yellow powder. A reddish-brown dust sometimes tinges the sails and rigging. An instance of this occurred on board the “Perry” on her outward bound passage, when five hundred miles from the African coast. The science of Ehrenberg has been searching amid the microscopic organisms contained in these substances, for tokens of their origin. In the red material he finds forms betraying not an African, but an American source, presumed to be in the great plains of the Amazon and Orinoco. This suggests new views of the meteorology of the world; but the theories founded on it, are not clear of mechanical difficulties. If we stand on almost any shore of the world as it exists at present, and consider the character of the land surface on the one hand, and of the ocean bottom on the other, we shall see that a very great difference in the nature of the beach line would be produced by a depression of the land towards the ocean, or by an elevation of it from the deep. The sea in its action on the bottom fills up hollows and obliterates precipices; but a land surface is worn into ravines and valleys. Hence a depression, so that the waters overflowed the land, would admit them into its recesses, and river courses, and winding gulleys--forming bays, islands, and secure harbors. Whereas elevation would bring up from the bottom its sand-banks and plains, forming an extent of slightly winding and unsheltered shore. The character of a coast will therefore depend very greatly upon its former history, before it became fixed. We have this contrast in the eastern and western sides of the Adriatic, or in the western and eastern sides of the British islands. These circumstances are to some degree controlled by the effects of partial volcanoes, or of powerful winds and currents. But on the whole, it may generally be inferred that a long unbroken shore indicates that the last change on the land level was one of elevation; while a coast penetrated, broken, and defended by islands has received its conformation from being stopped in the process of subsiding.