The Rio Negro is the largest and most celebrated of the black-water rivers. All its upper tributaries, the smaller ones especially, are very dark, and, when they run over white sand, give it the appearance of gold, from the rich colour of the water, which, when deep, appears inky black. In the rainy season, when the dark clouds above cause the water to appear of a yet more funereal blackness and the rising waves break in white foam over the vast expanse, the scene, as may well be imagined, is gloomy in the extreme.
The peculiar colour of the black-water rivers appears to be produced by the solution of decaying leaves, roots and other vegetable matter. In the virgin forests in which most of these streams have their source the little brooks and rivulets are half choked up with dead leaves and rotten branches giving various brown tinges to the water. When these rivulets meet together and accumulate into a river, they of course have a deep brown hue very similar to that of our bog or peat water, if there are no other circumstances to modify it. But if the stream flows through a district of soft alluvial clay, the colour will of course be modified and the brown completely overpowered.
A peculiarity of the black waters is the absence of mosquitos along their banks, which thus afford agreeable places of refuge to the persecuted traveller. No inducement will make an Indian boatman paddle so hard as the probability of reaching one of these privileged spots before midnight and being enabled to enjoy the comforts of sleep till morning.
The basin of the Amazons extending over an area of 2,330,000 English square miles surpasses in dimensions that of any other river in the world. All western Europe could be placed in it without touching its boundaries and it would even contain our whole Indian empire. It is entirely situated in the Tropics, on both sides of the Equator, and receives over its whole extent the most abundant rains. The body of fresh water which it empties into the ocean is therefore far greater than that of any other river; not only absolutely but probably also relatively to its area, for as it is almost entirely covered by dense virgin forests, the heavy rains which penetrate them do not suffer so much evaporation as when they fall on the scorched Llanos of the Orinoco or the treeless Pampas of La Plata.
Some idea may be formed of the vastness of the territory drained by the Amazons from the fact that at the sources of its northern and southern tributaries, the rainy season takes place at opposite times of the year. So wonderful is the length of the stream that, while at the foot of the Andes it begins to rise early in January, the Solimoens swells only in February: and below the Rio Negro the Amazons does not attain its full height before the end of March.
The swelling of the river is colossal as itself. In the Solimoens and farther westwards the water rises above forty feet; and Von Martius even saw trees whose trunks bore marks of the previous inundation fifty feet above the height of the stream during the dry season.
Then for miles and miles the swelling giant inundates his low banks, and, majestic at all times, becomes terrible in his grandeur when rolling his angry torrents through the wilderness. The largest forest-trees tremble under the pressure of the waters, and trunks, uprooted and carried away by the stream, bear witness to its power. Fishes and alligators now swim where a short while ago the jaguar lay in wait for the tapir, and only a few birds, perching on the highest tree-tops, remain to witness the tumult which disturbs the silence of the woods.
When at length the river retires within its usual limits, new islands have been formed in its bed, while others have been swept away; and in many places the banks, undermined by the floods, threaten to crush the passing boat by their fall,—a misfortune which not seldom happens, particularly when high trees come falling headlong down with the banks into the river.
The lands flooded to a great depth at every time of high water are called in the language of the country ‘Gapo,’ and are one of the most singular features of the Amazons. They extend hundreds of miles along the river’s course, and vary in width on each side from one to ten or twenty miles. Through the Gapo a person may go by canoe in the wet season, without once entering into the main river. He will pass through small streams, lakes, and swamps, and everywhere around him will stretch out an illimitable waste of waters, but all covered with a lofty virgin forest. For days he will travel through this forest scraping against the trunks of trees, and stooping to pass beneath the leaves of prickly palms now level with the water though raised on stems forty feet high. In this trackless maze the Indian finds his way with unerring certainty, and by slight indications of broken twigs or scraped bark goes on day by day as if travelling on a beaten road.
The magical beauty of tropical vegetation reveals itself in all its glory to the traveller who steers his boat through the solitudes of these aquatic mazes. Here the forest forms a canopy over his head; there it opens, allowing the sunshine to disclose the secrets of the wilderness; while on either side the eye penetrates through beautiful vistas into the depths of the woods. Sometimes, on a higher spot of ground, a clump of trees forms an island worthy of Eden. A chaos of bushropes and creepers flings its garlands of gay flowers over the forest, and fills the air with the sweetest odours. Numerous birds, rivalling in beauty of colour the passifloras and bignonias of these hanging gardens, animate the banks of the lagune, while gaudy macaws perch on the loftiest trees; and as if to remind one that death is not banished from this scene of paradise, a dark-robed vulture screeches through the woods, or an alligator rests, like a black log of wood or a sombre rock, on the dormant waters.