The blocks were lava and hard felsite, measuring one and a half to three feet.

As a rule, these trincheras had a lateral extent of thirty feet, and in the central part they were fifteen feet high.

After all the great labour expended in their construction, the builders of these terraces had secured in each only a space thirty feet long and fifteen feet wide; in other words, these eight terraces yielded together barely 3,000 square feet, which means space enough for planting five or six hundred hills of corn.

People who do not know the Indians would consider this too small a result to favour the theory that these terraces were erected for agricultural purposes.

But the Indian's farming is, in proportion to his wants, conducted on a small scale, and he never thinks of raising more corn than he actually needs; in fact, many tribes, as for instance the Tarahumares, seldom raise enough to last the family all the year through.
Further groups of cave-dwellings were found some ten miles higher up the river, in what is called the "Strawberry Valley," probably through the prevalence of the strawberry tree, of which several beautiful specimens were seen.