The alternation of deeps and shallows at this point in the river and the well-developed canyon meanders are among the most celebrated of their kind in the world. Though shut in by high cliffs and bordered by mountains the river exhibits a succession of curves so regular that one might almost imagine the country a plain from the pattern of the meanders. The succession of smooth curves for a long distance across existing mountains points to a time when a lowland plain with moderate slopes drained by strongly meandering rivers was developed here. Uplift afforded a chance for renewed down-cutting on the part of all the streams, and the incision of the meanders. The present meanders are, of course, not the identical ones that were formed on the lowland plain; they are rather their descendants. Though they still retain their strongly curved quality, and in places have almost cut through the narrow spurs between meander loops, they are not smooth like the meanders of the Mississippi. Here and there are sharp irregular turns that mar the symmetry of the larger curves. The alternating bands of hard and soft rock have had a large part in making the course more irregular. The meanders have responded to the rock structure. Though regular in their broader features they are irregular and deformed in detail.
Deeps and shallows are known in every vigorous river, but it is seldom that they are so prominently developed as in these great canyons. At one point in the upper canyon the river has been broadened into a lake two or three times the average width of the channel and with a scarcely perceptible current; above and below the “laguna,” as the boatmen call it, are big rapids with beds so shallow that rocks project in many places. In the Pongo de Mainique the river is at one place only fifty feet wide, yet so deep that there is little current. It is on the banks of the quiet stretches that the red forest deer grazes under leafy arcades. Here, too, are the boa-constrictor trails several feet wide and bare like a roadway. At night the great serpents come trailing down to the river’s edge, where the red deer and the wildcat, or so-called “tiger,” are their easy prey.
It is in such quiet stretches that one also finds the vast colonies of water skippers. They dance continuously in the sun with an incessant motion from right to left and back again. Occasionally one dances about in circles, then suddenly darts through the entire mass, though without striking his equally erratic neighbors. An up-and-down motion still further complicates the effect. It is positively bewildering to look intently at the whirling multitude and try to follow their complicated motions. Every slight breath of wind brings a shock to the organization of the dance. For though they dance only in the sun, their favorite places are the sunny spots in the shade near the bank, as beneath an overhanging tree. When the wind shakes the foliage the mottled pattern of shade and sunlight is confused, the dance slows down, and the dancers become bewildered. In a storm they seek shelter in the jungle. The hot, quiet, sunlit days bring out literally millions of these tiny creatures.
One of the longest deeps in the whole Urubamba lies just above the Pongo at Mulanquiato. We drifted down with a gentle current just after sunset. Shrill whistles, like those of a steam launch, sounded from either bank, the strange piercing notes of the lowland cicada, cicada tibicen. Long decorated canoes, better than any we had yet seen, were drawn up in the quiet coves. Soon we came upon the first settlement. The owner, Señor Pereira, has gathered about him a group of Machigangas, and by marrying into the tribe has attained a position of great influence among the Indians. Upon our arrival a gun was fired to announce to his people that strangers had come, upon which the Machigangas strolled along in twos and threes from their huts, helped us ashore with the baggage, and prepared the evening meal. Here we sat down with five Italians, who had ventured into the rubber fields with golden ideas as to profits. After having lost the larger part of their merchandise, chiefly cinchona, in the rapids the year before, they had established themselves here with the idea of picking rubber. Without capital, they followed the ways of the itinerant rubber picker and had gathered “caucho,” the poorer of the two kinds of rubber. No capital is required; the picker simply cuts down the likeliest trees, gathers the coagulated sap, and floats it down-stream to market. After a year of this life they had grown restless and were venturing on other schemes for the great down-river rubber country.
| Fig. 13—Composition of tropical vegetation in the rain forest above Pongo de Mainique, elevation 2,500 feet (760 m.). Scores of species occur within the limits of a single photograph. | Fig. 14—The mule trail in the rain forest between Rosalina and Pongo de Mainique. Each pool is from one and a half to two feet deep. Even in the dry season these holes are full of water, for the sunlight penetrates the foliage at a few places only. |