The post-houses in the desolate mountains between Arequipa and Puno are all of the same character. They consist of a range of low stone buildings surrounding a courtyard on three sides, and consisting of five or six rooms with mud floors, a rough table, and a platform of stone and mud at one end, which is intended for a bed-place. The roof is badly tiled or thatched, and the doors are so roughly fitted that it is impossible to close them. Both man and beast are subject to a most distressing illness, caused by the rarefaction of the air at these great altitudes, which is called _sorochi_ by the Peruvians. I had suffered from a sharp attack of illness at Arequipa, so that I was probably predisposed to a visitation from _sorochi_, which I certainly endured to its fullest extent. Before arriving at Apo, a violent pressure on the head, accompanied by acute pain, and aches in the back of the neck, caused great discomfort, and these symptoms increased in intensity during the night at the Apo post-house, so that at three A.M., when we recommenced our journey, I was unable to mount my mule without assistance. A ride of seven hours across grassy plains covered with herbage, with patches of snow here and there, and ranges of hills with fine masses of rocks, forming a setting to the distant peaks of the cordillera, brought us to the post-house of Pati. During this ride we had to ford the river, which flows past Arequipa as the Chile, more than a dozen times. The only living creatures are the _lecca-leccas_, a bird which frequents the numerous streams, and the graceful flocks of vicuñas. The _lecca-lecca_ is a large plover, with red legs, white head, grey body, white under the breast and tail, and wings and tail broadly edged with black. It incessantly utters a wild shrill scream. The vicuñas, a species of llama with the habits of an antelope, are very beautiful and graceful creatures. They have rich fawn-coloured coats, with patches of white across the shoulders and inside the legs, and long slender necks. They are constantly met with in the most desolate parts of the cordillera, browsing on the tender shoots of the tufts of _ychu_, or galloping along with their noses close to the ground, as if they were scenting out the best pasture. At Pati a range of abrupt porphyritic cliffs rises from the plain, up which a rough zigzag pass leads to the "Pampa de Confital,"[128] the loftiest part of the road over this pass of the cordillera. A storm of hail began to fall, which turned into snow as we reached the pampa, and a ride of many hours over a succession of wild desolate plains, in an incessant snow-storm, brought us to the "alto de Toledo," the highest part of the road, and 15,590 feet above the level of the sea.[129] Some glorious snowy peaks appeared through the gloom at sunset, and after several weary hours in the darkness we at length arrived at the post-house of Cuevillas.