Evidently these walls were built for the protection of the people in time of war.
About five miles south of our camping place the river turns eastward, and again two miles below this point it receives a tributary from the west.

One day I followed the broken cordon on its eastern bank, then turned north and ascended an isolated mountain, which rises about fifteen hundred feet high above the river.

There is a small level space on top, and on this there has been built, at some time, a fortress with walls of undressed stones from two to six feet high and three feet thick.

It was about fifty paces long in one direction, and about half that length in the other.

Remains of houses could be traced, and inside of the walls themselves the ground plan of three little chambers could be made out.
On the Bavispe River we photographed a trinchera which was about eight feet high and thirty feet long; and one of the foremen observed one which was at least fifteen feet high.
I decided to move the camp one and a half miles down the river, and to its right bank, on a cordon, where Mason, one of my Mexican foremen, had discovered some ruins.