Occasionally in the spring great masses of this detritus slide down the mountains, and cover the snow-drifts in the valleys, thus forming natural ice-houses.

We rode over one, the height of which was far below the limit of perpetual snow.
As the evening drew to a close, we reached a singular basin-like plain, called the Valle del Yeso.

It was covered by a little dry pasture, and we had the pleasant sight of a herd of cattle amidst the surrounding rocky deserts.

The valley takes its name of Yeso from a great bed, I should think at least 2000 feet thick, of white, and in some parts quite pure, gypsum.

We slept with a party of men, who were employed in loading mules with this substance, which is used in the manufacture of wine.