In considering the quantity of water which the Orinoco bears to the Atlantic, the question arises—Which of the great South American Rivers,—the Orinoco, the Amazons, or the River Plate,—is the largest? The question, however, thus put is not a determinate one, the idea of size in this case not being altogether definite. The River Plate has the widest embouchure, being 92 geographical miles across; but, like the British rivers, its length is comparatively small. Even at Buenos Ayres its depth is already so inconsiderable as to impede navigation. The Amazons is the longest of all rivers: its course from its origin in the Lake of Lauricocha to its mouth is 2880 geographical miles. But its breadth in the province of Jaen de Bracamoros, near the cataract of Rentama, as measured by me at the foot of the picturesque mountain of Patachuma, hardly equals that of the Rhine at Mayence.
The Orinoco is narrower at its mouth than either the River Plate or the Amazons; and its length, according to positions astronomically determined by me, only amounts to 1120 geographical miles. But, on the other hand, far in the interior of Guiana, 560 miles from its mouth, I still found its breadth, when full, 16200 Parisian (17265 Eng.) feet. The periodical swelling of the river annually raises its level at this part of its course from 30 to 36 feet above its lowest level. Sufficient materials for an accurate comparison of the enormous rivers which intersect the continent of South America are still wanting. For such a comparison it would be needful to know in each case the profile of the river-bed, and the velocity of the water, which differs very greatly in different parts of the same stream.
If, in the Delta enclosed by its variously divided and still unexplored arms,—in the regularity of its periodical rise and fall—and in the number and size of its crocodiles,—the Orinoco shews points of resemblance to the Nile, there is this further analogy between the two rivers, that after long rushing rapidly through many windings between wood-fringed shores formed by granitic and syenitic rocks and mountains, during the remainder of their course they slowly roll their waters to the sea, between treeless banks, over an almost horizontal bed. An arm of the Nile (the Green Nile, Bahr-el-Azrek) flows from the celebrated mountain-lake near Gondar, in the Abyssinian Gojam Alps, to Syene and Elephantis, through the mountains of Shangalla and Sennaar. In a similar manner the Orinoco rises on the southern declivity of the mountain chain which, in the 4th and 5th parallel of North latitude, extends westward from French Guiana towards the Andes of New Granada. The sources of the Orinoco[58] have never been visited by any European, or even by any natives who have been in communication with Europeans.
In ascending the Upper Orinoco in the summer of 1800, we passed the Mission of Esmeralda, and reached the mouths of the Sodomoni and the Guapo. Here rises high above the clouds the massive summit of the Yeonnamari or Duida, a grand and picturesque mountain which presents to the spectator one of the finest scenes of nature which the tropical world has to offer. Its altitude, according to my trigonometrical measurement, is 8278 (8823 Eng.) feet above the level of the sea. The southern slope of the mountain presents a treeless grassy surface, and the humid evening air is filled far and wide with the fragrance of the ripe ananas. The stalks of the pine apples, swelling with rich juice, rise between the lowly herbs of the meadow, and the golden fruit is seen shining at a distance from under its leafy crown of bluish-green. Where mountain springs or rivulets break forth from the turfy covering, the scene is further adorned by groups of tall fan-palms, whose foliage never feels the influence of a cool breeze.
On the east of the Duida mountain a dense thicket of wild Cacao groves begins, and amidst these are found trees of the celebrated Bertholletia excelsa, the most vigorous of the productions of the tropical world[59]. Here the Indians collect the materials for their blow-pipes, colossal grass-stalks having joints above 18 feet long from knot to knot.[60] Some Franciscan monks have penetrated as far as the mouth of the Chiguire, where the river is already so narrow that the natives have thrown across it, near the waterfall of the Guaharibes, a suspension bridge formed of the twining stems of climbing plants. The Guaicas, a race of comparatively light complexion but of small stature, armed with poisoned arrows, forbid any farther advance towards the east.
All, therefore, that has been put forward respecting the lake origin of the Orinoco is fabulous[61]. We seek in vain in nature for the Laguna of El Dorado, which is still marked in Arrowsmith’s maps as an inland sea 80 geographical miles in length. Has the little reedy lake of Amucu, from which the Pirara (a branch of the Mahu) flows, given rise to this fable? But the swamp in which the lake of Amucu is situated is four degrees of longitude to the east of the district in which the sources of the Orinoco must be sought.
It was an ancient custom of dogmatising geographers to make all the larger rivers of the world originate in considerable lakes. To the lake forming the supposed origin of the Orinoco was transferred the site of the island of Pumacena, a rock of micaceous slate, the glitter of which, in the 16th century, played, in the fable of El Dorado, a memorable, and to deceived humanity often a fatal part. It is the belief of the natives, that the Magellanic clouds of the southern hemisphere, and even the fine nebulæ in the constellation of the ship Argo, are a reflection of the metallic brilliancy of the silver mountains of the Parime.
The Orinoco is one of those rivers which, after many windings, seem to return back towards the region in which they took their rise. After following a westerly and then a northerly course, it runs again to the east, so that its mouth is almost in the same meridian as its source. From the Chiguire and the Gehette as far as the Guaviare the Orinoco flows to the west, as if it would carry its waters to the Pacific. It is in this part of its course that it sends out towards the south a remarkable arm, the Cassiquiare, but little known in Europe, which unites with the Rio Negro, (called by the natives the Guainia), and offers perhaps the only example of a bifurcation forming in the very interior of a continent a natural connection between two great rivers and their basins.
The nature of the ground, and the junction of the Guaviare and Atabapo with the Orinoco, cause the latter to turn suddenly towards the north. In the absence of correct geographical knowledge, the Guaviare flowing in from the west was long regarded as the true origin of the Orinoco. The doubts raised by an eminent geographer, M. Buache, since 1797, as to the probability of a connection with the Amazons, have I hope been entirely refuted by my expedition. In an uninterrupted navigation of 920 geographical miles I passed through the singular network of rivers, from the Rio Negro, by the Cassiquiare, into the Orinoco; traversing in this manner the interior of the Continent, from the Brazilian boundary to the coast of Caraccas.
In the upper portion of the basin of the Orinoco and its tributaries, between the 3rd and 4th degrees of north latitude, nature has several times repeated the enigmatical phenomenon of the so-called “black waters.” The Atabapo, whose banks are adorned with Carolinias and arborescent Melastomas, and the Temi, Tuamini, and Guainia, are all rivers of a coffee-brown colour. In the shade of the palm groves this colour seems almost to pass into ink-black. When placed in transparent vessels, the water appears of a golden yellow. The image of the Southern Constellations is reflected with wonderful clearness in these black streams. Where their waters flow gently, they afford to the observer, when taking astronomical observations with reflecting instruments, a most excellent artificial horizon. A cooler atmosphere, less torment from stinging mosquitoes, greater salubrity, and the absence of crocodiles (fish, however, are also wanting), mark the region of these black rivers. They probably owe their peculiar colour to a solution of carburetted hydrogen, to the luxuriance of the tropical vegetation, and to the quantity of plants and herbs on the ground over which they flow. On the western declivity of the Chimborazo, towards the coast of the Pacific, I remarked that the flooded waters of the Rio de Guayaquil gradually assumed a golden yellow or almost coffee-brown colour, when covering the meadows for some weeks.