Chapter 43

The Valley of the Amazon.--Its Physical Geography.--Geology.--Climate.--Vegetation.

From the Atlantic shore to the foot of the Andes, and from the Orinoco to the Paraguay, stretches the great Valley of the Amazon. In this vast area the United States might be packed without touching its boundaries. It could contain the basins of the Mississippi, the Danube, the Nile, and the Hoang-Ho. It is girt on three sides by a wall of mountains: on the north are the highlands of Guiana and Venezuela; on the west stand the Andes; on the south rise the table-lands of Matto Grosso. The valley begins at such an altitude, that on the western edge vegetation differs as much from the vegetation at Pará, though in the same latitude, as the flora of Canada from the flora of the West Indies.

The greater part of the region drained by the Amazon, however, is not a valley proper, but an extensive plain. From the mouth of the Napo to the ocean, a distance of eighteen hundred miles in a straight line, the slope is one foot in five miles.[159] At Coca, on the Napo, the altitude is 850 feet, according to our observations; at Tinga Maria. on the Huallaga, it is 2200 according to Herndon; at the junction of the Negro with the Cassiquiari, it is 400 according to Wallace; at the mouth of the Marmoré, it is 800 according to Gibbon; at the Pongo de Manseriche, below all rapids, it is 1160 according to Humboldt; and at the junction of Araguaia with the Tocantíns, it is 200 according to Castelnau. These barometrical measurements represent the basin of the Amazon as a shallow trough lying parallel to the equator, the southern side having double the inclination of the northern, and the whole gently sloping eastward. Farthermore, the channel of the great river is not in the centre of the basin, but lies to the north of it: thus, the hills of Almeyrim rise directly from the river, while the first falls on the Tocantíns, Xingú, and Tapajos are nearly two hundred miles above their mouths; the rapids of San Gabriel, on the Negro, are one hundred and seventy-five miles from the Amazon, while the first obstruction to the navigation of the Madeira is a hundred miles farther from the great river.

[Footnote 159: Professor Agassiz gives the average slope as hardly more than a foot in ten miles, which is based on the farther assertion that the distance from Tabatinga to the sea-shore is more than 2000 miles in a straight line. The distance is not 1600, or exactly 1500, from Pará.--See _A Journey in Brazil_, p. 349.]

Of the creation of this valley we have already spoken. No region on the face of the globe of equal extent has such a monotonous geology. Around the rim of the basin are the outcroppings of a cretaceous deposit; this rests on the hidden mezozoic and palæozoic strata which form the ribs of the Andes. Above it, covering the whole basin from New Granada to the Argentine Republic,[160] are the following formations: first, a stratified accumulation of sand; second, a series of laminated clays, of divers colors, without a pebble; third, a fine, compact sandstone; fourth, a coarse, porous sandstone, so ferruginous as to resemble bog iron-ore. This last was, originally, a thousand feet in thickness, but was worn down, _perhaps_, in some sudden escape of the pent-up waters of the valley. The table-topped hills of Almeyrim are almost the sole relics.[161] Finally, over the undulating surface of the denuded sandstone an ochraceous, unstratified sandy clay was deposited.

[Footnote 160: Messrs. Myers and Forbes found this red clay on the Negro, most abundantly near Barcellos; also in small quantities on the Orinoco above Maipures. The officers of the "Morona" assured us that the same formation was traceable far up the Ucayali and Huallaga. This clay from the Amazon, as examined microscopically by Prof. H. James Clark, contains fragments of gasteropod shells and bivalve casts. The red earth of the Pampas, according to Ehrenberg, contains eight fresh-water to one salt-water animalcule.]

[Footnote 161: "On the South American coast, where tertiary and supra-tertiary beds have been extensively elevated, I repeatedly noticed that the uppermost beds were formed of coarser materials than the lower; this appears to indicate that, as the sea becomes shallower, the force of the waves or currents increased."--Darwin's _Observations_, pt. ii., 131. "Nowhere in the Pampas is there any appearance of much superficial denudation."--Pt. iii., 100.]

It is a question to what period this great accumulation is to be assigned. Humboldt called it "Old Red Sandstone;" Martius pronounced it "New Red;" Agassiz says "Drift"--the glacial deposit brought down from the Andes and worked over by the melting of the ice which transported it.[162] The Professor farther declares that "these deposits are fresh-water deposits; they show no sign of a marine origin; no sea-shells nor remains of any marine animal have as yet been found throughout their whole extent; tertiary deposits have never been observed in any part of the Amazonian basin." This was true up to 1867. Neither Bates, Wallace, nor Agassiz found any marine fossil on the banks of the great river. But there is danger in building a theory on negative evidence. These explorers ascended no farther than Tabatinga. Two hundred miles west of that fort is the little Peruvian village of Pebas, at the confluence of the Ambiyacu. We came down the Napo and Marañon, and stopped at this place. Here we discovered a fossiliferous bed intercalated between the variegated clays so peculiar to the Amazon. _It was crowded with marine tertiary shells!_ This was Pebas _vs_. Cambridge. It was unmistakable proof that the formation was not drift, but tertiary; not of fresh, but salt water origin. The species, as determined by W.M. Gabb, Esq., of Philadelphia, are: _Neritina pupa, Turbonilla minuscula_, _Mesalia Ortoni_, _Tellina Amazonenis_, _Pachydon obliqua_, and _P. tenua_.[163] All of these are new forms excepting the first, and the last is a new genus. It is a singular fact that the _Neritina_ is now living in the West India waters, and the species found at Pebas retains its peculiar markings. So that we have some ground for the supposition that not many years ago there was a connection between the Caribbean Sea and the Upper Amazon; in other words, that Guiana has only very lately ceased to be an island. There is no mountain range on the water-shed between the Orinoco and the Negro and Japurá, but the three rivers are linked by natural canals.[164] Interstratified with the clay deposit are seams of a highly bituminous lignite; we traced it from near the mouth of the Curaray on the Rio Napo to Loreto on the Marañon, a distance of about four hundred miles. It occurs also at Iquitos. This is farther testimony against the glacial theory of the formation of the Amazonian Valley. The paucity of shells in such a vast deposit is not astonishing. It is as remarkable in the similar accumulation of reddish argillaceous earth, called "Pampean mud," which overspreads the Rio Plata region.[165] Some of the Pampa shells, like those at Pebas, are proper to brackish water, and occur only on the highest banks. The Pampean formation is believed by Mr. Darwin to be an estuary or delta deposit. We will mention, in this connection, that silicified wood is found at the head waters of the Napo; the Indians use it instead of flint (which does not occur there) in striking a light. Darwin found silicified trees on the same slope of the Andes as the Uspallata Pass.

[Footnote 162: _A Journey in Brazil_, p. 250, 411, 424. Again, in his Lecture before the Lowell Institute, 1866: "These deposits could not have been made by the sea, nor in a large lake, as they contain no marine nor fresh-water fossils."]

[Footnote 163: These interesting fossils are figured and described in the _Am. Journal of Conchology_.]

[Footnote 164: "The whole basin between the Orinoco and the Amazon is composed of granite and gneiss, slightly covered with débris. There is a total absence of sedimentary rocks. The surface is often bare and destitute of soil, the undulations being only a few feet above or below a straight line."--Evan Hopkins, in _Quart. Jour. Geol. Soc_., vol. vi.]

[Footnote 165: See Darwin on the absence of extensive modern conchiferous deposits in South America, _Geological Observations_, pt. iii., ch. v.]

The climatology of the Valley of the Amazon is as simple as its physical geography. There is no circle of the seasons as with us--nature moves in a straight line. The daily order of the weather is uniform for months. There is very little difference between the dry and hot seasons; the former, lasting from July to December, is varied with showers, and the latter, from January to June, with sunny days, while the daily temperature is the same within two or three degrees throughout the year. On the water-shed between the Orinoco and Negro it rains throughout the year, but most water falls between May and November, the coolest season in that region. On the Middle Negro the wet season extends from June 1st to December 1st, and is the most sultry time.

Comparatively few insects, birds, or beasts are to be seen in summer; but it is the harvest-time of the inhabitants, who spend the glorious weather rambling over the plaias and beaches, fishing and turtle-hunting. The middle of September is the midsummer of the valley. The rainy season, or winter, is ushered in by violent thunder-storms from the west. It is then that the woods are eloquent with buzzing insects, shrill cicadas, screaming parrots, chattering monkeys, and roaring jaguars. The greatest activity of animal and vegetable life is in June and July. The heaviest rains fall in April, May, and June. Scarcely ever is there a continuous rain for twenty-four hours. Castelnau witnessed at Pebas a fall of not less than thirty inches in a single storm. The greatest amount noticed in New York during the whole month of September was 12.2 inches. The humidity of the atmosphere, as likewise the luxuriance of vegetation and the abundance and beauty of animal forms, increases from the Atlantic to the Andes. At the foot of the Andes, Poeppig found that the most refined sugar in a few days dissolved into sirup, and the best gunpowder became liquid even when inclosed in canisters. So we found the Napo steaming with vapor. Fogs, however, are rarely seen on the Amazon.

The animals and plants are not all simultaneously affected by the change of seasons. The trees retain their verdure through the dry _vera[=o]_, and have no set time for renewing their foliage. There are a few trees, like Mongruba, which drop their leaves at particular seasons; but they are so few in number they create the impression of a few dead leaves in a thick-growing forest. Leaves are falling and flowers drooping all the year round. Each species, and, in some cases, each individual, has its own particular autumn and spring. There is no hibernation nor æstivation (except by land shells); birds have not one uniform time for nidification; and moulting extends from February to May.

Amazonia, though equatorially situated, has a temperate climate. It is cooler than Guinea or Guiana. This is owing to the constant evaporation from so much submerged land, and the ceaseless trade winds. The mean annual temperature of the air is about 81°.[166] The nights are always cool. There are no sudden changes, and no fiery "dog days." Venereal and cutaneous affections are found among the people; but they spring from an irregular life. A traveler on the slow black tributaries may take the tertiana, but only after weeks of exposure. Yellow fever and cholera seldom ascend the river above Pará; and on the Middle Amazon there are neither endemics nor epidemics, though the trades are feebly felt there, and the air is stagnant and sultry. According to Bates, swampy and weedy places on the Amazon are generally more healthy than dry ones. Whatever exceptions be taken to the branches, the main river is certainly as healthy as the Mississippi: the rapid current of the water and the continual movement of the air maintaining its salubrity. The few English residents (Messrs. Hislop, Jeffreys, and Hauxwell), who have lived here thirty or forty years, are as fresh and florid as if they had never left their native country. The native women preserve their beauty until late in life. Great is the contrast between the gloomy winters and dusty summers, the chilly springs and frosty autumns of the temperate zone, and the perennial beauty of the equator! No traveler on the Amazon would exchange what Wallace calls "the magic half-hour after sunset" for the long gray twilight of the north. "The man accustomed to this climate (wrote Herndon) is ever unwilling to give it up for a more bracing one."

[Footnote 166: Agassiz calls the average temperature 84°, which, it seems to us, is too high. The mean between the temperatures of Pará, Manáos, and Tabatinga is 80.7°.]

The mineral kingdom is represented only by sand, clay, and loam. The solid rock (except the sandstone already mentioned) begins above the falls on the tributaries. The precious gems and metals are confined to the still higher lands of Goyaz, Matto Grosso, and the slopes of the Andes. The soil on the Lower Amazon is sandy; on the Solimoens and Marañon it is a stiff loam or vegetable mould, in many places twenty feet deep.

Both in botany and zoology, South America is a natural and strongly-marked division, quite as distinct from North America as from the Old World; and as there are no transverse barriers, there is a remarkable unity in the character of the vegetation. No spot on the globe contains so much vegetable matter as the Valley of the Amazon. From the grassy steppes of Venezuela to the treeless Pampas of Buenos Ayres, expands a sea of verdure, in which we may draw a circle of eleven hundred miles in diameter, which shall include an ever green, unbroken forest. There is a most bewildering diversity of grand and beautiful trees--a wild, unconquered race of vegetable giants, draped, festooned, corded, matted, and ribboned with climbing and creeping plants, woody and succulent, in endless variety. The exuberance of nature displayed in these million square acres of tangled, impenetrable forest offers a bar to civilization nearly as great as its sterility in the African deserts. A _macheta_ is a necessary predecessor: the moment you land (and it is often difficult to get a footing on the bank), you are confronted by a wall of vegetation. Lithe lianas, starred with flowers, coil up the stately trees, and then hang down like strung jewels; they can be counted only by myriads, yet they are mere superfluities. The dense dome of green overhead is supported by crowded columns, often branchless for eighty feet. The reckless competition among both small and great adds to the solemnity and gloom of a tropical forest. Individual struggles with individual, and species with species, to monopolize the air, light, and soil. In the effort to spread their roots, some of the weaker sort, unable to find a footing, climb a powerful neighbor, and let their roots dangle in the air; while many a full-grown tree has been lifted up, as it were, in the strife, and now stands on the ends of its stilt-like roots, so that a man may walk upright between the roots and under the trunk.[167]

[Footnote 167: Buttress roots are not peculiar to any one species, but common to most of the large trees in the crowded forest, where the lateral growth of the roots is made difficult by the multitude of rivals. The Paxiuba, or big-bellied palm, is a fine example.]

The mass of the forest on the banks of the great river is composed of palms (about thirty species[168]), leguminous or pod-bearing trees, colossal nut-trees, broad-leaved Musaceæ or bananas, and giant grasses. The most prominent palms are the architectural Pupunha, or "peach-palm," with spiny stems, drooping, deep green leaves, and bunches of mealy, nutritious fruit; the slender Assaï, with a graceful head of delicate green plumes; the Ubussú, with mammoth, undivided fronds; the stiff, serrated-leaved Bussú, and gigantic Mirití. One of the noblest trees of the forest is the Massaranduba, or "cow-tree" (_Brosimum galactodendron_), often rising one hundred and fifty feet. It is a hard, fine-grained, durable timber, and has a red bark, and leathery, fig-like foliage. The milk has the consistency of cream, and may be used for tea, coffee, or custards. It hardens by exposure, so as to resemble gutta-percha. Another interesting tree, and one which yields the chief article of export, is the Caucho, or India-rubber tree[169] (_Siphonia Brasiliensis_), growing in the lowlands of the Amazon for eighteen hundred miles above Pará. It has an erect, tall trunk, from forty to eighty feet high, a smooth, gray bark, and thick, glossy leaves. The milk resembles thick, yellow cream, and is colored by a dense smoke obtained by burning palm-nuts. It is gathered between August and December. A man can collect six pounds a day, though this is rarely done. It is frequently adulterated with sand. The tree belongs to the same apetalous family as our castor-oil and the mandioca; while the tree which furnishes the caoutchouc of the East Indies and Africa is a species of Ficus, and yields an inferior article to the rubber of America. Other characteristic trees are the Mongruba, one of the few which shed their foliage before the new leaf-buds expand; the giant Samaüma, or silk-cotton tree (called _huimba_ in Peru); the Calabash, or _cuieira_, whose gourd-like fruit furnishes the cups used throughout the Amazon; the Itauba, or stone-wood, furnishing ship-timber as durable as teak; the red and white Cedar, used for canoes (not coniferous like the northern evergreen, but allied to the mahogany); the Jacarandá, or rose-wood, resembling our locust; Palo de sangre, one of the most valuable woods on the river; Huacapú, a very common timber; Capirona, used as fuel on the steamers; and Tauarí, a heavy, close-grained wood, the bark of which splits into thin leaves, much used in making cigarettes. The Piassaba, a palm yielding a fibre extensively manufactured into cables and ropes, and exported to foreign countries for brushes and brooms, being singularly elastic, strong, and more durable than hemp; and the Moira-pinima, or "tortoise-shell wood," the most beautiful wood in all Amazonia, if not in the world, grow on the Upper Rio Negro. A small willow represents the great catkin family.

[Footnote 168: Von Martius, in his great work on the Brazilian Palms, enumerates in all 582 species.]

[Footnote 169: The Portuguese and Brazilians call it _seringa_, or syringe, in which form it is still used extensively, injections forming a great feature in the popular system of cures. The tree mentioned above yields most of the rubber of commerce, and is considered distinct from the species in Guiana, _S. elastica;_ while the rubber from the Upper Amazon and Rio Negro comes from the _S. lutea_ and _S. brevifolia_. Agassiz puts milk-weed in the same family!]

The valley is as remarkable for the abundance, variety, and value of its timber as for any thing else. Within an area of half a mile square, Agassiz counted one hundred and seventeen different kinds of woods, many of them eminently fitted, by their hardness, tints, and beautiful grain, for the finest cabinet-work. Enough palo de sangre or moira-pinima is doubtless wasted annually to veneer all the palaces of Europe.

While most of our fruits belong to the rose family, those of the Amazon come from the myrtle tribe. The delicious flavor, for which our fruits are indebted to centuries of cultivation, is wanting in many of the torrid productions. We prefer the sweetness of Pomona in temperate climes to her savage beauty in the sunny south. It is a curious fact, noticed by Herndon, that nearly all the valuable fruits of the valley are inclosed in hard shells or acid pulps. They also reach a larger size in advancing westward. The common Brazil nut is the product of one of the tallest trees in the forest (_Bertholletia excelsa_). The fruit is a hard, round shell, resembling a common ball, which contains from twenty to twenty-four nuts. Eighteen months are required for the bud to reach maturity. This tree, says Humboldt, offers the most remarkable example of high organic development. Akin to it is the Sapucaya or "chickens' nuts" (_Lecythis sapucaya_), whose capsule has a natural lid, and is called "monkey's drinking-cup." The nuts, about a dozen in number, are of irregular shape and much richer than the preceding. But they do not find their way to market, because they drop out of the capsule as soon as ripe, and are devoured by peccaries and monkeys. The most luscious fruit on the Amazon is the atta of Santarem. It has the color, taste, and size of the chirimoya; but the rind, which incloses a rich, custardly pulp, frosted with sugar, is scaled. Next in rank are the melting pine-apples of Pará, and the golden papayas, fully equal to those on the western coast. This is the original home of the cacao. It grows abundantly in the forests of the upper river, and particularly on the banks of the Madeira. The wild nut is smaller but more oily than the cultivated. The Amazon is destined to supply the world with the bulk of chocolate. The aromatic tonka beans (Cumarú) used in flavoring snuff, and the Brazilian nutmegs (Puxiri), inferior to the Ceylon, grow on lofty trees on the Negro and Lower Amazon. The Guaraná beans are the seeds of a trailing plant; from these the Mauhés prepare the great medicine, on the Amazon, for diarrhoea and intermittent fevers. Its active principle, caffeine, is more abundant than in any other substance, amounting to 5.07 per cent.; while black tea contains only 2.13. Coffee, rice, tobacco, and sugar-cane are grown to a limited extent. Rio Negro coffee, if put into the market, would probably eclipse that of Ceará, the best Brazilian. Wild rice grows abundantly on the banks of the rivers and lakes. The cultivated grain is said to yield forty fold. Most of the tobacco comes down from the Marañon and Madeira. It is put up in slender rolls from three to six feet long, tapering at each end, and wound with palm fibre. The sugar-cane is an exotic from Southeastern Asia, but grows well. The first sugar made in the New World was by the Dutch in the island of St. Thomas, 1610. Farina is the principal farinaceous production of Brazil. The mandioca or cassava (_Manihot utilissima_) from which it is made is supposed to be indigenous, though it is not found wild. It does not grow at a higher altitude than 2000 feet. Life and death are blended in the plant, yet every part is useful. The cattle eat the leaves and stalks, while the roots are ground into pulp, which, when pressed and baked, forms farina, the bread of all classes. The juice is a deadly poison: thirty-five drops were sufficient to kill, in six minutes, a negro convicted of murder; but it deposits a fine sediment of pure starch that is the well-known tapioca; and the juice, when fermented and boiled, forms a drink. On the upper waters grow the celebrated coca, a shrub with small, light-green leaves, having a bitter, aromatic taste. The powdered leaves, mixed with lime, form _ypadú_. This is to Peruvians what opium is to the Turk, betel to the Malay, and tobacco to the Yankee. Thirty million pounds are annually consumed in South America. It is not, however, an opiate, but a powerful stimulant. With it the Indian will perform prodigies of labor, traveling days without fatigue or food. Von Tschudi considers its moderate consumption wholesome, and instances the fact that one coca-chewer attained the good old age of one hundred and thirty years; but when used to excess it leads to idiocy. The signs of intemperance are an uncertain step, sallow complexion, black-rimmed, deeply-sunken eyes, trembling lips, incoherent speech, and stolid apathy. Coca played an important part in the religious rights of the Incas, and divine honors were paid to it. Even to-day the miners of Peru throw a quid of coca against the hard veins of ore, affirming that it renders them more easily worked; and the Indians sometimes put coca in the mouth of the dead to insure them a welcome in the other world. The alkaloid cocaïne was discovered by Wöhler.

Flowers are nearly confined to the edges of the dense forest, the banks of the rivers and lagunes. There are a greater number of species under the equator, but we have brighter colors in the temperate zone. "There is grandeur and sublimity in the tropical forest (wrote Wallace, after four years of observation), but little of beauty or brilliancy of color." Perhaps the finest example of inflorescence in the world is seen in the _Victoria Regia_, the magnificent water-lily discovered by Schömberg in 1837. It inhabits the tranquil waters of the shallow lakes which border the Amazon. The leaves are from fifteen to eighteen feet in circumference, and will bear up a child twelve years old; the upper part is dark, glossy green, the under side violet or crimson. The flowers are a foot in diameter, at first pure white, passing, in twenty-four hours, through successive hues from rose to bright red. This queen of water-plants was dedicated to the Queen whose empire is never at once shrouded in night.