Between the more easterly paralleling ranges great rivers run, having their birth in the snow-cap and incessant rains, both of which are the result of the deposition from the moisture-laden trade winds which, sweeping across the Atlantic and Brazil for thousands of miles, are intercepted by the crest of the Cordillera, impinging thereon and depositing their moisture. Running down the easterly slope, in a thousand rills, the waters gather in the giant channels, all flowing northwards, in the troughs between the ranges, to where, with curious regularity, they break through these ranges in deep cuttings or _pongos_, as they are there termed, like gargantuan mill-races, turning thus east and pouring forth their floods upon the Amazon plain, where, after vast courses amid the forests, they reach the main stream of the Amazon, and finally empty themselves on the coast of Brazil into the Atlantic, whence they originally came upon the wings of the wind--a mighty natural hydraulic engine, unceasing in its operations, stupendous in its work. Yes; _Siste, viator_, draw rein-- Hast thou entered the treasures of the snow? Or hast thou seen the treasuries of the hail? Who hath cleft a channel for the water-flood? Dost thou know the balancings of the clouds? The imprint of the Andes perhaps never fades from the mind of the traveller. When you have braved the tempest and the steep, when your slow and panting beast overcomes the last few rising yards upon the maritime range that shuts off from view the White Cordillera, then, as the dark horizon of the foreground rocks gives place, your astonished gaze rests upon that range of white-clothed sentinels beyond, upraised some time since the Jurassic or Silurian Ages. There they mark the eras: there they stand, performing their silent and allotted work; and there, when evening falls, it tints their brows with orange and with carmine, and wraps their bases with the purple pall of finished day. Borne upward three to five miles above the level of the ocean arose these mighty guardians of the western shore, carrying some ocean bed from where it lay, where strange creatures of the deep reposed within the ooze--huge ammonites and cephalopods, whose fossil scrolls and circles, now petrified in rigid schools upon the stiffened summits, catch the traveller's eye as his weary mule stumbles over the limestone ridges: and, blurred by the pelting rain of the Andine winter and loosened from the stony grasp by frost and sun and earthquake, they, together with the rocky walls that hold them, are again dissolving into particles; a phase within the endless sequence of Nature's work; an accident of her ceaseless and inexplicable operations.