The active principle of the coca-leaf has, a few years ago, been separated by Dr. Niemann, and called _cocaine_. Pure _cocaine_ crystallizes with difficulty, is but slightly soluble in water, but is easily dissolved in alcohol, and still more easily in ether.[325] I chewed coca, not constantly, but very frequently, from the day of my departure from Sandia, and, besides the agreeable soothing feeling it produced, I found that I could endure long abstinence from food with less inconvenience than I should otherwise have felt, and it enabled me to ascend precipitous mountain-sides with a feeling of lightness and elasticity, and without losing breath. This latter quality ought to recommend its use to members of the Alpine Club, and to walking tourists in general, though the sea voyage would probably cause the leaves to lose much of their virtue. To the Peruvian Indian, however, who can procure it within a few weeks of its being picked, the coca is a solace which is easily procured, which affords great enjoyment, and which has a most beneficial effect.[326] CHAPTER XV. CARAVAYA. Chinchona forests of Tambopata. ON the morning of April 27th we crossed a rude bridge over the Huari-huari, and began to make our way up the face of the steep mountain on the other side, first through a thick forest, and then up into the grassy highlands, until, after several halts, we at length reached the summit of the ridge, though a mountain-peak still rose up in our rear. From this point there was a most extensive panoramic view. A sea of ridges rose one behind the other, with stupendous snowy peaks in the background, and, more than a thousand feet below, the rivers of Sandia and Huari-huari, reduced to mere glittering threads, could be seen winding through the tortuous ravines. We had now reached the _pajonales_, and were on a ridge or back-bone between the rivers of Laccani and San Lorenzo, two tributaries of the Huari-huari; a grass-covered and comparatively cold region, interspersed with thickets, forming the crest of the tropical forests which line the sides of the ravines through which the rivers wind, far below. When there is sunshine, these _pajonales_ form a very pleasant landscape: the broad expanse of grass, dotted over with a graceful milk-white flower called _sayri-sayri_, is intersected by dense thickets, some in the gullies and watercourses, and others in clumps, like those in an English park, the palms and tree-ferns raising their graceful heads above the rest of the trees. Here and there a black pool of sweet water is met with at the edge of the thicket, with chinchona and _huaturu_-trees drooping over it. Everywhere there is an abrupt boundary to the foreground in the profound forest-covered ravines, with splendid views of mountain ranges in the distance.