At length a day came when the noble river, upon the broad bosom of which they had journeyed for so many days, dwindled to a tiny brook brawling over a rocky bed, across which they could leap, the forest grew thin and stunted, degenerated to a few scattered scrub oaks, and finally ceased altogether, and they found themselves confronted by a mountain barrier, the bare rocks of which were interspersed with patches of grass, upon some of which were grazing small flocks of most extraordinary animals, such as they had never seen before, but with which Vilcamapata was evidently quite familiar. There were three distinct species of them, although they all bore a striking resemblance to each other, being about the size of donkeys, but having long necks, heads somewhat like those of sheep, and legs and feet resembling those of camels. Vilcamapata informed the Englishmen that these animals were known respectively as alpacas, llamas, and vicunas, and that the first were used by his countrymen for food, while their wool was woven into garments; the second were used as beasts of burden, and the third were valuable principally for their hair and hides. The river was now left behind; but this caused the travellers no inconvenience, for the mountains which they were ascending, were most of them snow-capped, and tiny rivulets of ice-cold water, formed by the melting snow, were frequently met with, so that they were at no loss for water wherewith to quench their thirst. But as they pressed on, climbing ever higher and higher, they began to suffer very severely, first from cold, and next from mountain sickness, due to the steadily increasing rarefaction of the atmosphere. Vilcamapata, however, had a remedy for both evils, for he killed three alpacas and stripped off their skins to serve as wraps for himself and his companions, to protect them from the cold; while, as soon as the first symptoms of mountain sickness declared themselves, he produced from his pouch a quantity of leaves of the marvellous coca, and bade the Englishmen chew them, which they did; whereupon not only did the sickness disappear, but they felt no further need of food, while their strength was restored to them in a manner that seemed absolutely miraculous. It cost them three days of arduous labour to cross this mountain range; but the evening of the third day found them once more encamped in the tropical forest beside a tiny stream that flowed to the southward and eastward, while, on the farther side, the valley sloped away into a still deeper depression.