It was my intention, after marking down all the eligible plants of the shrubby _Calisaya_, to be taken up on our return, to make for the forest-covered valley of Tambopata, which is full of chinchona-trees; and I therefore left the ravine of the Sandia river at this point, and, by a rapid descent, went down from the grassy uplands to a region of tropical forest, full of palms and tree-ferns. We thus reached the banks of the Huari-huari. This river flows through a deep and very narrow ravine, lined with forest, for about 500 feet, above which rise grassy mountains to an immense height. Though only 30 feet across, and confined by dark polished rocks, the Huari-huari is very deep, and decidedly a more important stream than the Sandia, at their junction. We established ourselves under a rock, where there was no room to pitch the tent, and thus our first night of camping out commenced, for previously we had slept in the road-side _tambos_. The Indians carried little earthen pots for cooking, in their _ccepis_, and got up a fire of dry sticks with great rapidity. I had a delicious bath in the river, where the tall forest trees overshadowed the water on either side. At night the moon streamed its floods of light over the forest, and the brilliant sparks from myriads of fire-flies shone from the trees in every direction up the side of the opposite mountain; but in the early morning the sky clouded over, and a heavy drizzling rain began to fall, which prevented sleep, and made us wish for day. From this encampment our way led up the precipitous sides of the mountain, to the grassy _pajonales_ which divide the valleys of Sandia and Tambopata; but I will here halt awhile to give a brief account of the cultivation of that plant, of which we had lately seen so much, and which enabled me to ascend the mighty passes of the Andes on foot with ease and comfort--the strength-giving, invigorating coca. A general geographical description of all this country has been given in the preceding chapter. During my stay at Sandia the indications of the thermometer were as follows, between the 20th and 25th of April:-- Mean temperature 63-1/5° Minimum temperature at night 50-1/2 Highest observed 65 Lowest 47 Range 18 CHAPTER XIV. COCA-CULTIVATION.