Guerreros is at the head of the gorge leading down to Islay; and, from a rising ground a little beyond the tambo,[122] the great desert of Arequipa opens upon the view, bounded by a range of mountains which are crowned by the snowy peak of the volcano. At this point there is a wooden cross which marks the grave of a poor soldier belonging to the fugitive army of Salaverry, in 1836, who, worn out with fatigue and thirst, had here sunk down to die, and had been lightly covered over with sand. The flesh was in perfect preservation. We then entered the great desert of Arequipa, extending to the horizon on the right and left, and ending in front at the foot of the rocky range of mountains separating the sandy waste from the fertile campiña of Arequipa. The desert consists of hard ground, without a blade of vegetation, affording good riding; but it is covered at short intervals with mounds of the finest white sand, from twenty to thirty feet high, all in the shape of a half-moon, with their horns pointing north-west, and thus denoting the prevailing wind. They are called _Medanos_. These _Medanos_ shift their positions, and the breeze, whirling the sand in eddies on their summits, often causes a singing noise in the early dawn. Frequently they form athwart the road, which has to deviate in a half-circle, and rejoin the old track on the other side; but they all resemble each other exactly, and afford no landmark to the lost or benighted traveller. In the centre of the desert is the post-house or tambo of La Joya, twenty miles from Guerreros, kept by an Englishman, whose homely name of Jimmy Eyres has been converted into the more grandiloquent and euphonious Spanish one of Don Santiago Casimiro de los Ayres. Water and fodder for the beasts are brought from a great distance, and their price is of course proportionately high; but, considering its position in the midst of a desert and many leagues from all supplies, the little tambo, consisting of several rooms of deal planking roughly knocked together, was very comfortable.