From this, the first day of our forest-life, until the 14th of May, being just a fortnight, we were actively engaged in the examination of the chinchona region, and in the collection of plants. As the best way of recording the results of our investigations, I now propose to give a detailed account of our proceedings from day to day; and, in the following chapter, to recapitulate our observations with special reference to the climate, soil, and general habit of those species of chinchonæ which came immediately under our notice. I owe much to the intelligent assistance of our guide Martinez, who, to great experience in woodcraft, added a lynx's eye for a _Calisaya_-plant; and it required no little quickness and penetration to distinguish these treasures, amidst the close entanglement of the undergrowth, in the dense forests. Martinez spoke Spanish very imperfectly, and, without a knowledge of Quichua, I should have found much difficulty in conversing with him; but he had a most complete and thorough knowledge of all forest-lore, and was acquainted with the native name of almost every plant, and with the uses to which they were or might be applied. At dawn the Indians found the marks of a jaguar on the beach close to the tent; and a huge snake wriggled through the fallen trees as we re-entered the forest. The brilliant colours and great variety of butterflies were very striking. I particularly noticed one, bright blue and crimson above, with the underside marked with a pattern, as if drawn by a crow-quill on a snow-white ground, edged with deep blue. After struggling through the forest for about a mile we came to the foot of the tremendous precipices, one on either side of the river, which Martinez called Ccasa-sani. That on our (the western) shore rises up perpendicularly from the water to a height which we estimated at 500 feet, ending in a rocky peak. Its sides are masses of bare polished rock, except in the rear, and in some crevices, where vegetation finds a foothold. Amongst other trees the paccay (_Mimosa Inga_), with its cottony fruit, was drooping over the bubbling waves. The river, surging furiously over and around huge masses of rock, dashed noisily on between the two precipices.