Cataracts of the Orinoco. —A foaming surface of four miles in length presents itself at once to the eye: iron-black masses of rock resembling ruins and battlemented towers rise frowning from the waters. Rocks and islands are adorned with the luxuriant vegetation of the tropical forest; a perpetual mist hovers over the waters, and the summits of the lofty palms pierce through the cloud of spray and vapour. When the rays of the glowing evening sun are refracted in these humid exhalations a magic optical effect begins. Coloured bows shine, vanish, and reappear; and the ethereal image is swayed to and fro by the breath of the sportive breeze. During the long rainy season the streaming waters bring down islands of vegetable mould, and thus the naked rocks are studded with bright flowerbeds adorned with Melastomas and Droseras, and with small silver-leaved mimosas and ferns. These spots recall to the recollection of the European those blocks of granite decked with flowers which rise solitary amidst the glaciers of Savoy, and are called by the dwellers in the Alps “Jardins,” or “Courtills.” In the blue distance the eye rests on the mountain chain of Cunavami, a long extended ridge which terminates abruptly in a truncated cone. We saw the latter (Calitamini in its Indian name) glowing at sunset as if in roseate flames. This appearance returns daily: no one has ever been near the mountain to detect the precise cause of this brightness, which may perhaps proceed from a reflecting surface produced by the decomposition of talc or mica slate. During the five days which we passed in the neighbourhood of the cataracts, it was striking to hear the thunder of the rushing torrents sound three times louder by night than by day. In all European waterfalls the same phenomenon is remarked. What can be its cause in a wilderness where there is nothing to interrupt the repose of nature! Perhaps the currents of heated ascending air, by causing irregular density in the elastic medium, impede the propagation of sound during the day, by the disturbance they may occasion in the waves of sound; whereas during the nocturnal cooling of the earth’s surface the upward currents cease.— Humboldt’s Aspects of Nature.