When we consider the great mass of water poured into the Atlantic Ocean by the Orinoco, we are naturally led to ask which of the South American rivers is the greatest—the Orinoco, the Amazon, or the La Plata? The question is as indeterminate as the idea of greatness itself. The Rio de la Plata has undoubtedly the widest mouth, its width measuring 92 miles across; but this river, like those of Great Britain, is comparatively of but inconsiderable length. Its shallowness, too, is so great as to impede navigation at Buenos Ayres. The Amazon, which is the longest of all rivers, measures 2880 miles from its rise in the Lake of Lauricocha to its estuary. Yet its width in the province of Jaen de Bracamoros, near the cataract of Rentama, where I measured it at the foot of the picturesque mountain of Patachuma, is scarcely equal to that of the Rhine at Mayence. The Orinoco is narrower at its mouth than either the La Plata or the Amazon, while its length, according to my astronomical observations, does not exceed 1120 geographical miles. But in the interior of Guiana, 560 miles from its estuary, I found that at high water the width of the river measured upwards of 17,265 feet. Its periodical swelling here raises the level of the waters every year from 30 to 36 feet above the lowest water-mark. We are still without sufficient data for an accurate comparison between the enormous rivers which traverse the South American Continent. For such a comparison it would be necessary to ascertain the profile of the river-bed, as well as the velocity of the water, which varies very considerably at different points. If the Orinoco, in the Delta formed by its variously divided and still unexplored branches, as well as in the regularity of its rise and fall, and in the number and size of its crocodiles, exhibits numerous points of resemblance to the Nile; there is this further analogy between the two rivers, that they for a long distance wind their impetuous way, like forest torrents, between granitic and syenitic rocks, till, slowly rolling their waters over an almost horizontal bed, skirted by treeless banks, they reach the sea. An arm of the Nile (the Green Nile, Bahr-el-Azrek), from the celebrated mountain lake, near Gondar, in the Gojam Alps, in Abyssinia, to Syene and Elephantis, winds its way through the mountain range of Schangalla and Sennar; and in like manner the Orinoco rises on the southern slope of a mountain chain, which stretches between the parallels of 4° and 5° north lat., from French Guiana, in a westerly direction towards the Andes of New Granada. The sources of the Orinoco have never been visited by any European[58], nor even by any natives who have held intercourse with Europeans.