ridden on a
continuous though gradual ascent since sunrise. My panting mule
slackened his pace, and seemed unwilling to mount a rather steep ascent
which we had now arrived at. To relieve him I dismounted, and began
walking at a rapid pace. But I soon felt the influence of the rarefied
atmosphere, and I experienced an oppressive sensation which I had never
known before. I stood still for a few moments to recover myself, and
then tried to advance; but an indescribable oppression overcame me. My
heart throbbed audibly; my breathing was short and interrupted. A
world's weight seemed to lie upon my chest; my lips swelled and burst;
the capillary vessels of my eyelids gave way, and blood flowed from
them. In a few moments my senses began to leave me. I could neither see,
hear, nor feel distinctly. A grey mist floated before my eyes, and I
felt myself involved in that struggle between life and death which, a
short time before, I fancied I could discern on the face of nature. Had
all the riches of earth, or the glories of heaven, awaited me a hundred
feet higher, I could not have stretched out my hand towards them.

In this half senseless state I lay stretched on the ground, until I felt
sufficiently recovered to remount my mule. One of the Puna storms was
now gathering, thunder and lightning accompanied a heavy fall of snow,
which very soon lay a foot deep on the ground. In a short time I
discovered that I had missed my way. Had I then known the Puna as well
as I afterwards did, I should have shaped my course by the flight of
birds. But unluckily I pursued the fresh track of a herd of vicunas,
which led me directly into a swamp. My mule sank, and was unable to
extricate himself. I was almost in despair. Nevertheless, I cautiously
alighted, and with incredible difficulty I succeeded in digging out with
a dagger the mud in which the animal's legs were firmly fixed, and at
length I got him back to a solid footing. After wandering about in
various directions, I at length recovered the right path, which was
marked by numerous skeletons protruding above the snow. These were the
remains of beasts of burthen, which had perished on their journeys; a
welcome, though an ominous guide to the wandering traveller. The clouds
now suddenly separated, and the blazing light of the tropical sun glared
dazzlingly on the white plain of snow. In a moment I felt my eyes
stricken with _surumpe_.

Suffering the most violent pain, and tormented by th