I visited the banks of the Irura and the rich woods accompanying it, and two other streams in the same neighbourhood, one called the Panema, and the other the Urumari, once or twice a week during the whole time of my residence in Santarem, and made large collections of their natural productions.These forest brooks, with their clear, cold waters brawling over their sandy or pebbly beds through wild tropical glens, always had a great charm for me.The beauty of the moist, cool, and luxuriant glades was heightened by the contrast they afforded to the sterile country around them.The bare or scantily wooded hills which surround the valley are parched by the rays of the vertical sun.One of them, the Pico do Irura, forms a nearly perfect cone, rising from a small grassy plain to a height of 500 or 600 feet, and its ascent is excessively fatiguing after the long walk from Santarem over the campos.I tried it one day, but did not reach the summit.Adense growth of coarse grasses clothed the steep sides of the hill, with here and there a stunted tree of kinds found in the plain beneath.In bared places, a red crumbly soil is exposed;and in one part a mass of rock, which appeared to me, from its compact texture and the absence of stratification, to be porphyritic; but I am not geologically sufficient to pronounce on such questions.Mr.Wallace states that he found fragments of scoriae, and believes the hill to be a volcanic cone.To the south and east of this isolated peak, the elongated ridges or table-topped hills attain a somewhat greater elevation.
The forest in the valley is limited to a tract a few hundred yards in width on each side the different streams; in places where these run along the bases of the hills, the hillsides facing the water are also richly wooded, although their opposite declivities are bare or nearly so.The trees are lofty and of great variety; amongst them are colossal examples of the Brazil nut tree (Bertholletia excelsa), and the Pikia.This latter bears a large eatable fruit, curious in having a hollow chamber between the pulp and the kernel, beset with hard spines which produce serious wounds if they enter the skin.The eatable part appeared to me not much more palatable than a raw potato; but the inhabitants of Santarem are very fond of it, and undertake the most toilsome journeys on foot to gather a basketful.The tree which yields the tonka bean (Dipteryx odorata), used in Europe for scenting snuff, is also of frequent occurrence here.It grows to an immense height, and the fruit, which, although a legume, is of a rounded shape, and has but one seed, can be gathered only when it falls to the ground.A considerable quantity (from 1000to 3000 pounds) is exported annually from Santarem, the produce of the whole region of the Tapajos.An endless diversity of trees and shrubs, some beautiful in flower and foliage, others bearing curious fruits, grow in this matted wilderness.It would be tedious to enumerate many of them.I was much struck with the variety of trees with large and diversely-shaped fruits growing out of the trunk and branches, some within a few inches of the ground, like the cacao.Most of them are called by the natives Cupu, and the trees are of inconsiderable height.One of them called Cupu-ai bears a fruit of elliptical shape and of a dingy earthen colour six or seven inches long, the shell of which is woody and thin, and contains a small number of seeds loosely enveloped in a juicy pulp of very pleasant flavour.The fruits hang like clayey ants'-nests from the branches.Another kind more nearly resembles the cacao; this is shaped something like the cucumber, and has a green ribbed husk.It bears the name of Cacao de macaco, or monkey's chocolate, but the seeds are smaller than those of the common cacao.I tried once or twice to make chocolate from them.They contain plenty of oil of similar fragrance to that of the ordinary cacao-nut, and make up very well into paste; but the beverage has a repulsive clayey colour and an inferior flavour.
