1. RIVER VIEW ON MAIN STREAM NEAR ISSA RIVER
2. LANDSCAPE ON UPPER AMAZON MAIN STREAM
The Igara Parana runs into the Issa where that river makes a horse-shoe bend,[11] the junction being on the inner side of the horse-shoe. The breadth of the stream at its mouth is 161 metres. The water is clearer than that of the Issa, and the current slower, never more than 3 miles an hour. Some 220 miles upstream there is an important waterfall, known as La Chorrera, or the Big Falls. The Igara Parana becomes vary narrow and most tortuous as it nears them, and is only 30 metres wide at its exit from Big Falls Bay. This is a huge pool almost as wide as it is long, with a narrow exit at one end, and a succession of cascades at the other. These falls are impassable in boats, and traffic with the upper river can only be carried on by land portage. Much debris of rocks and river-borne tree-trunks obstructs the narrow passage above the falls, which are given by Robuchon as having a total length of 120 metres and a width of 18 metres. The waters descend over a series of wide rocky steps, worn flat and smooth by the ceaseless friction. Masses of stone line the right bank, and rise perpendicularly from the water. This is the only part of the country where I have seen rocks and stones in any quantity.
The upper reaches of the river are distinctly more picturesque than its lower waters. The almost level banks, with their monotonous succession of forest trees, grow gradually steeper, till the sandstone cliffs rise like a fortification above the fringe of vegetation that encroaches on the high-water mark. Presently the river winds in and out between shelving hills, tree-clad to the very margin of the water. Between the Igara Parana and the Kara Parana the country is a perfect switchback of hills and ridges, with a stream in every gully. The steepness of these valleys, with a pitch perhaps of 25° or 30°, does not permit the surface water to lodge and form swamp or morass, in contrast to the waterlogged plains of the lower rivers. Immediately on the left bank of the Igara Parana, and in the vicinity of the Big Falls, the country continues to be hilly, but to the north-east it is more open, and the bush is less obstructive, though its density varies immensely. Similar diversified scenery is to be found on the upper waters of the Japura.
The Kahuanari, a considerable tributary on the south bank of the Japura, drains the divide that intervenes between that river and the Igara Parana. It is subject to sudden floods, which wash down large quantities of forest debris. I have seen it rise twenty feet in a day, and afterwards subside as quickly.
The floods are not to be wondered at when the tremendous rainfall of these regions is considered. The question is never if it will rain, but when and for how long it will be fine. Rain is certain in a land which has but a few days clear of it in every twelve months. Five days, a fortnight, that, all told, is the extent of dry weather to be looked for in this country. The dry season is but a name. It is dry only in comparison with the wetter months from March to August. The upper valley of the Amazon has a three-day winter at our midsummer—June 24, 25, 26—so it is said, and certainly I noted a very decided drop in the temperature of these days in 1908. Snow is unknown, and hail not common. Despite the daily rain the turquoise blue of the sky is seldom long hidden, though from March to June leaden skies portend rain, and seldom fail to make good their portent. During the dry season the rain if it be frequent is never continuous. Almost every day, between three and four in the afternoon and two and five in the morning, heavy clouds will roll up, a preliminary breeze rustle through the leaves, shake the trees, and increase till suddenly there comes a deluge of big drops. Such storms last but half an hour, yet the rain will soak through everything, and the wet bushes drench the passer-by for hours afterwards. Nothing is ever really dry, things are in a constant state of saturation, and it is possible at all times to wring moisture out of any of one’s belongings. So great and incessant is the evaporation that at night the dew is as heavy as rain, while the marshy low-lying lands and the rivers are shrouded by mist both morning and evening. With such humid air lichens and Hepaticæ flourish on all the tree-trunks, though I have never seen them, as described by Spruce, covering the very leaves of the trees.[12]
Electric disturbances are numerous, and a sharp and sudden thunder-shower often occurs about three in the afternoon, or in the night, though rain at night without thunder is common. These storms come up in the dry season especially, and the worst storms may be expected in February, at the breaking of the dry weather. Sometimes the electric storm will consist of an uninterrupted display of lightning with little or no thunder, and the sizzle of light makes the landscape appear as in a cinematograph picture. This continued on one occasion all through the night, and from the amount of interest the Indians evinced I judged it to be an unusual occurrence.
It is always possible to tell when rain will come because of the preliminary breeze, hardly felt below the tree-tops, followed by a dead calm that precedes the downpour. The prevailing wind for nine months of the year will be from the east or south-east, from June to August it will be north and north-west. In January the prevailing wind is from the Atlantic, north-east, veering to south-west; in July from the Pacific, south-west, round to north-east. Fitful and uncertain local whirlwinds will, without warning, swoop down on the clearings round the houses, play havoc in forest and plantation, uproot trees, and destroy habitations.
In spite of the continual rain, of the universal humidity; the climate is not unhealthy. The heat, though a damp heat, is never excessive, the enormously great evaporation brings in a succession of fresh breezes to moderate the temperature;[13] and so, despite apparently trying conditions, the climate is not injurious. The low watersheds between the large rivers appear to be quite healthy, and if there be fever its prevalence varies locally to an extraordinary degree. It has been observed that where the soil is first turned up fever not infrequently follows, a fact noted in other parts of the world, and by no means a condition peculiar to the Amazons.
The soil of the vast Amazonian basin is mainly the alluvial deposit of decomposed vegetable life for centuries past. This sea of Pampean mud stretches from the ocean marshes up to the very heels of the mountains that stand outpost to hold the southern continent from the Pacific. Black and rich it lies in layer after layer twenty, thirty, forty feet beneath the great pall of vegetation that flourishes above during its little day, to die and drop for successive generations of arboreal life to thrive upon in their turn. And in all this vastness is never a stone. Vegetable mould and water-borne mud, but stone does not exist for thousands upon thousands of miles. Only in the upper waters of the Amazonian system are rock formations reached; in the particular district under consideration nothing is to be found harder than a soft, friable sandstone. On parts of the Issa, as on the Napo, the deep banks show strata of shingle, with perhaps red or white clay, that alternate with the dark humus and decaying wood.