Certainly the exertion of walking was extremely great, and the respiration became deep and laborious: I am told that in Potosi (about 13,000 feet above the sea) strangers do not become thoroughly accustomed to the atmosphere for an entire year.

The inhabitants all recommend onions for the puna; as this vegetable has sometimes been given in Europe for pectoral complaints, it may possibly be of real service:--for my part I found nothing so good as the fossil shells! When about half-way up we met a large party with seventy loaded mules.

It was interesting to hear the wild cries of the muleteers, and to watch the long descending string of the animals; they appeared so diminutive, there being nothing but the black mountains with which they could be compared.

When near the summit, the wind, as generally happens, was impetuous and extremely cold.

On each side of the ridge we had to pass over broad bands of perpetual snow, which were now soon to be covered by a fresh layer.