Their climate is hardly less bleak and winterly than that of the high snow-ridges which bound them on either side. Cold winds sweep almost constantly over their surface, and during four months of the year they are daily visited by fearful storms. The suddenly darkened sky discharges, under terrific thunder and lightning, enormous masses of snow, until the sun breaks forth again. But soon the clouds obscure its brilliancy; and thus winter and summer, here reign alternately,-- not, as in our temperate climes, during several months, but within the short space of a single day. In a few hours the change of temperature often amounts to forty or forty-five degrees, and the sudden fall of the thermometer is rendered still more disagreeable to the traveller by biting winds, which so violently irritate the skin of the hands and face, that it springs open and bleeds from every fissure. An intolerable burning and swelling accompany these wounds, so as to prevent the use of the hands for several days. On the lips it is also very disagreeable, as the pain increases by eating and speaking; and an incautious laugh produces deep rents, which bleed for a long time and heal with difficulty. This evil, which is called _Chuñu_ by the Peruvian Indians, is also very painful on the eyelids; but it becomes absolutely insupportable by the addition of the _Surumpe_, a very acute and violent inflammation of the eyes, caused by the sun’s reflection from the snow. In consequence of the rarefied air and the biting winds, the visual organs are constantly in a state of irritation, which renders them far more sensitive to any strong light than would be the case in a more congenial atmosphere. The rapid change from a clouded sky to the brilliancy of a sunny snow-field, causes a painful stinging and burning, which increases from minute to minute to such a degree, that even the stoical Indian, when afflicted with this evil, will sit down on the road-side and utter cries of anguish and despair. Chronical ophthalmia, suppuration of the eyelids, and total blindness, are the frequent consequences of an intense surumpe, against which the traveller over the high lands carefully guards himself by green spectacles or a dark veil.