Then the high timber that usually skirts the rivulets shrinks to detached groves, and patches of clear land appear, which, if cultivated, would afford scanty support to one or two modern families.

To the village Indian such tillable spots were of the greatest value.

The deep ravine afforded shelter not only against the climate but against roving enemies, and the land was sufficient for his modest crops; since his wants were limited, and game was abundant.
The material of which the walls of these canons are composed, suggested in times past to the house-building Indian the idea of using them as a home.

The tufa and pumice-stone are so friable that, as we have said, the rock can be dug or burrowed with the most primitive implements.

It was easier, in fact, to excavate dwellings than to pile up walls in the open air.
Therefore the northern sides of these secluded gorges are perforated in many places by openings similar in appearance to pigeon-holes.