COMPOUNDING THE misery wrought by the rain was an overarching sense of isolation and uncertainty, a feeling that was magnified by strange noises that shattered the forest’s silence and set the men’s nerves on edge. That afternoon, as Roosevelt and the men in his dugout paddled quietly down the river, a long, deep shriek suddenly ripped through the jungle. It was the roar of a howler monkey, one of the loudest cries of any animal on earth. The sound, which can be heard from three miles away, is formed when the monkey forces air through its large, hollow hyoid bone, which sits between its lower jaw and voice box and anchors its tongue. The result is a deep, resonating howl that vibrates through the forest with strange, inhuman intensity, and echoes so pervasively that its location can be nearly impossible to identify.
Worse even than the noises they could recognize were those that none of them could explain. These strange sounds, which disappeared as quickly as they came and were a mystery even to those who knew the rain forest best, had made a strong impression on the British naturalist Henry Walter Bates fifty years earlier. “Often, even in the still hours of midday, a sudden crash will be heard resounding afar through the wilderness, as some great bough or entire tree falls to the ground,” the naturalist wrote. “There are, besides, many sounds which it is impossible to account for. I found the natives generally as much at a loss in this respect as myself. Sometimes a sound is heard like the clang of an iron bar against a hard, hollow tree, or a piercing cry rends the air; these are not repeated, and the succeeding silence tends to heighten the unpleasant impression which they make on the mind.”…
The Amazon’s sudden, inexplicable sounds were especially terrifying at night, when they were all in the pitch-black forest, with no way to see a potential attacker and no sure means of escape. While the jungle in daylight could sometimes appear completely devoid of inhabitants, the nightly cacophony left no doubt that the men of the expedition were not alone. Even for veteran outdoorsmen like George Cherrie, the setting of the sun came to mark an unnerving threshold between the relative familiarity of a long day on the river, and sleepless nights in the jungle, spent trying to imagine the source of the spine-chilling noises that echoed in the darkness around him. “Frequently at night, with my camp at the edge of the jungle,” he wrote, “I have lain in my hammock listening, my ears yearning for some familiar sound—every sense alert, nerves taut. Strange things have happened in the night.”
The screams, crashes, clangs, and cries of the long Amazon night were all the more disturbing because they often provoked apparent terror among the unseen inhabitants of the jungle themselves. In the fathomless canyons of tree trunks and the shrouds of black vines that surrounded the men at night, the hum and chatter of thousands of nocturnal creatures would snap into instant silence in response to a strange noise, leaving the men to wait in breathless apprehension of what might come next.
“Let there be the least break in the harmony of sound,” Cherrie observed, “and instantly there succeeds a deathlike silence, while all living things wait in dread for the inevitable shriek that follows the night prowler’s stealthy spring.”
Daily Archives: 20 March 2007
Each of the Amazon’s thousands of tributaries starts at a high point—either in the Andes, the Brazilian Highlands, or the Guiana Highlands—and then steadily loses elevation and picks up speed until it begins to approach the Amazon Basin. Scientists have divided these tributaries into three broad categories—milky, black, and clear—in reference to the color that they take on while carving their way through three different types of terrain. Alfred Russel Wallace, British naturalist and friend of Henry Walter Bates and Charles Darwin, made the distinction widely known in the mid-nineteenth century when he published his Narrative of Travels on the Amazon and Rio Negro. Wallace noted the striking difference between the milky Amazon and the black waters of the Negro where they collide on the northern bank of the Amazon. Seen from above, the meeting of these two colossal rivers looks like black ink spilling over parchment paper. The visual effect is heightened because the Negro, which is warmer and thus lighter in weight, rides on top of the Amazon, and the rivers do not fully blend until they have traveled dozens of miles together downstream.
Milky rivers, such as the Amazon and the Madeira, generally have their origins in the west and are clouded by the heavy sediment load that they carry down from the youthful Andes. Blackwater rivers, on the other hand, usually come from the ancient Guiana Highlands in the north and so wash over nutrient-poor, sandy soils. Scoured by millions of years of hard rains, these soils cannot retain decomposing organic matter—mostly leaves—which, when swept into a river, literally stains the water black like tea.
Although during the rainy season the River of Doubt is nearly as black as the Negro and as murky as the Amazon, it is technically a clearwater river. Like the Amazon’s largest clearwater rivers, the Tapajos and the Xingu, it has its source in the Brazilian Highlands, and so it picks up very little sediment as it flows over ancient and highly eroded soil. Clearwater rivers are also less acidic than blackwater rivers. Some, most notably the Tapajos, are so clear that they look blue, perfectly mirroring the sky above them. But most, like the River of Doubt, mix with either blackwater or milky tributaries as they snake through the rain forest, and so look neither blue nor clear by the time they reach their mouth.