Into their currents the hills and uplands pour their streams; to them the little rivulets come laughing and singing down from their sources in the forest depths.

A drop falling from a passing shower into the lake of Delolo may be carried eastward, through the Zambesi, to the Indian Ocean, or westward, along the transcontinental course of the Congo, to the Atlantic.

The mists that rise from great streams, separated by vast stretches of territory, commingle in the upper air, and are carried by vagrant winds to the wheat-fields of the far Northwest or the rice-fields of the South.

The ocean ceaselessly makes the circuit of the globe, and summons its tributaries along all shores to itself.

But it gives even more lavishly than it receives; day and night there rise over its vast expanse those invisible clouds of moisture which diffuse themselves through the atmosphere, and descend at last upon the earth to pour, sooner or later, into the rivers, and be returned whence they came.