THE RAPIDS AND CANYONS OF THE URUBAMBA 17 



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 low- 

 land 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 re- 

 sponded 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 in- 

 cessant 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 posi- 

 tively 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 



