IN the region of the cordillera of the Andes, in Northern and Central Peru, the country is broken up into deep warm valleys and profound ravines, separated by lofty precipitous ridges and snowy peaks, which combine to form some of the most magnificent scenery in the world. Vast flocks of sheep and alpacas find pasture on the upland slopes, while abundance of wheat is grown lower down. Indian corn generally flourishes at a still lower elevation, though it is grown as high as 13,000 feet on the islands of lake Titicaca, and sugar-cane is cultivated in the deep valleys. This is the nature of the country between Ayacucho and Cuzco, and in the valley of Vilcamayu, which extends from the foot of the Vilcañota range until it subsides into the vast tropical plains to the north and east of Cuzco. But the southern part of the interior of Peru, and the northern portion of Bolivia, present a very different character. From the Vilcañota mountains the Andes separate into two distinct chains, namely, the cordillera or coast-range, and the Eastern Andes, which include the loftiest peaks in South America, Illimani and Sorata, or Illampu. The region between these two ranges contains the great lake of Titicaca, and consists of elevated plains intersected by rivers flowing into the lake, at a height never less than 12,000 feet above the sea. The magnificent scenery of Northern and Central Peru is wanting in this southern part of the country, which composes the department of Puno, and is usually called the _Collao_. It, however, possesses features of its own which are at once striking and imposing, while the land which is drained by the lake of Titicaca was the cradle of the civilization of the Incas. The journey up the "Alto de los huesos" is very fatiguing, and the change from the pleasant exhilarating air of Chihuata, to the chilling icy blasts which constantly sweep over the upper region of the cordillera, was severely felt. As the afternoon advanced a drizzling mist came on, and added to the cheerless desolation of the plains it was necessary to traverse before reaching the post-house of Apo. Occasionally a drove of llamas, with their Indian driver, loomed for a moment through the mist, and at nightfall we arrived at the post-house of Apo (14,350 feet), tired, drenched, and cold. The rainy season of the cordilleras commences in November, and continues until the end of March, and during most of that time the discomfort of travelling is so great, and the rivers so swollen, that a journey is seldom undertaken by an ordinary traveller. In March, however, the rain does not fall continuously or in any quantity. The early morning is generally clear, but in the afternoon mists, rain, or snow begin to fall, and continue until far into the night. From April until October is the dry season, and in May, June, July, and August a cloud is scarcely ever seen in the sky.