Every plant, even the smaller ones, curls and writhes to the green surface, twining itself round its stronger and taller brethren in the effort. Climbing plants are monstrous and luxuriant, but others which have never been known to climb elsewhere learn the art as an escape from that somber shadow, so that the common nettle, the jasmine, and even the jacitara palm tree can be seen circling the stems of the cedars and striving to reach their crowns. Of animal life there was no movement amid the majestic vaulted aisles which stretched from us as we walked, but a constant movement far above our heads told of that multitudinous world of snake and monkey, bird and sloth, which lived in the sunshine, and looked down in wonder at our tiny, dark, stumbling figures in the obscure depths immeasurably below them. At dawn and at sunset the howler monkeys screamed together and the parrakeets broke into shrill chatter, but during the hot hours of the day only the full drone of insects, like the beat of a distant surf, filled the ear, while nothing moved amid the solemn vistas of stupendous trunks, fading away into the darkness which held us in. Once some bandy-legged, lurching creature, an ant-eater or a bear, scuttled clumsily amid the shadows. It was the only sign of earth life which I saw in this great Amazonian forest.
And yet there were indications that even human life itself was not far from us in those mysterious recesses. On the third day out we were aware of a singular deep throbbing in the air, rhythmic and solemn, coming and going fitfully throughout the morning. The two boats were paddling within a few yards of each other when first we heard it, and our Indians remained motionless, as if they had been turned to bronze, listening intently with expressions of terror upon their faces.
"What is it, then?" I asked.
"Drums," said Lord John, carelessly; "war drums. I have heard them before."
"Yes, sir, war drums," said Gomez, the half-breed. "Wild Indians, bravos, not mansos; they watch us every mile of the way; kill us if they can."
"How can they watch us?" I asked, gazing into the dark, motionless void.
The half-breed shrugged his broad shoulders.
"The Indians know. They have their own way. They watch us. They talk the drum talk to each other. Kill us if they can."
By the afternoon of that day--my pocket diary shows me that it was Tuesday, August 18th--at least six or seven drums were throbbing from various points. Sometimes they beat quickly, sometimes slowly, sometimes in obvious question and answer, one far to the east breaking out in a high staccato rattle, and being followed after a pause by a deep roll from the north. There was something indescribably nerve-shaking and menacing in that constant mutter, which seemed to shape itself into the very syllables of the half-breed, endlessly repeated, "We will kill you if we can. We will kill you if we can." No one ever moved in the silent woods. All the peace and soothing of quiet Nature lay in that dark curtain of vegetation, but away from behind there came ever the one message from our fellow-man. "We will kill you if we can," said the men in the east. "We will kill you if we can," said the men in the north.
All day the drums rumbled and whispered, while their menace reflected itself in the faces of our colored companions. Even the hardy, swaggering half-breed seemed cowed. I learned, however, that day once for all that both Summerlee and Challenger possessed that highest type of bravery, the bravery of the scientific mind. Theirs was the spirit which upheld Darwin among the gauchos of the Argentine or Wallace among the head-hunters of Malaya. It is decreed by a merciful Nature that the human brain cannot think of two things simultaneously, so that if it be steeped in curiosity as to science it has no room for merely personal considerations. All day amid that incessant and mysterious menace our two Professors watched every bird upon the wing, and every shrub upon the bank, with many a sharp wordy contention, when the snarl of Summerlee came quick upon the deep growl of Challenger, but with no more sense of danger and no more reference to drum-beating Indians than if they were seated together in the smoking-room of the Royal Society's Club in St. James's Street.