The Cataracts of Orinoco.

—A foamingsurface of four miles in length presents itself at once tothe eye: iron-black masses of rock resembling ruinsand battlemented towers rise frowning from the waters.Rocks and islands are adorned with the luxuriantvegetation of the tropical forest; a perpetual misthovers over the waters, and the summits of the loftypalms pierce through the cloud of spray and vapour.When the rays of the glowing evening sun are refractedin these humid exhalations a magic optical effect begins.Coloured bows shine, vanish, and reappear; and theethereal image is swayed to and fro by the breath of thesportive breeze. During the long rainy season thestreaming waters bring down islands of vegetable mould,and thus the naked rocks are studded with bright flower-beds adorned with Melastomas and Droseras, and with smallsilver-leaved mimosas and ferns. These spots recall tothe recollection of the European those blocks of granitedecked with flowers, which rise solitary amidst theglaciers of Savoy, and are called by the dwellers in the Alps “Jardins,” or “Courtills.” In the blue distance the eyerests on the mountain chain of Cunavami, a long ex-tended ridge which terminates abruptly in a truncatedcone. We saw the latter (Calitamini in its Indian name)glowing at sunset as if in roseate flames. This appear-ance returns daily: no one has ever been near themountain to detect the precise cause of this brightness,which may perhaps proceed from a reflecting surface pro-duced by the decomposition of talc or mica slate. Duringthe five days which we passed in the neighbourhood ofthe cataracts, it was striking to hear the thunder of therushing torrents sound three times louder by night thanby day. In all European waterfalls the same phenomenonis remarked. What can be its cause in a wildernesswhere there is nothing to interrupt the repose of nature?Perhaps the currents of heated ascending air by causingirregular density in the elastic medium, impede the pro-pagation of sound during the day, by the disturbancethey may occasion in the waves of sound; whereasduring the nocturnal cooling of the earth’s surfacethe upward currents cease.— Humboldt’s Aspects ofNature.