of the Mancos. Here there are two towers on the very edge of the mesa, so close that the outer walls are not complete, but are open toward the cliff. In the smaller of these towers, the outer wall is twenty-two feet in diameter, the inner twelve feet. In the larger tower, the diameters of the walls are respectively one hundred and forty and one hundred and twenty-three feet. Both are much broken down, so that the original height can not be estimated. In the face of the cliff, directly beneath these towers, are several cave-dwellings connected with the top of the cliff by steps cut in its face.
In the cañon of the Mancos, on the river-bottom, are the ruins of a large tower, the diameters of whose walls are respectively forty-three and twenty-five feet.
On a low bench near the McElms, a dry cañon which heads in the plateau, and enters the San Juan below the mouth of the Mancos, is a large settlement. On one side of the town is a large tower, remarkable as having triple walls, whose diameters are respectively forty-five, thirty-five, and fifteen feet. The space between the outer and middle walls is divided by partition-walls, while that between the middle and inner walls is not. In this and all other such structures there are no openings through the walls into the interior apartment. Access to it was had probably through a subterranean passage, as has been observed in at least one case.
Connected with the agricultural and mesa towns are, in many cases, watch-towers usually of circular form, perched on fragments of rocks in commanding positions, whence the approach of enemies can be detected. These are small and with single walls. In the neighborhood of some agricultural settlements are holes dug in the earth, and the earth thrown up in heaps in front, as in rifle-pits. They probably were made for a similar use.
The rocks of which the cañon cliffs are composed are of sandstone and shale. The former is hard and is acted on by the elements slowly, while the latter is easily disintegrated. Hence it is common to find that strata pathways up the cliff have disintegrated faster than those above and below, leaving horizontal crevices of greater or less height and depth. These crevices have been utilized by these people, when hard pressed by their enemies, as strongholds. They built walls across the whole fronts, leaving only little holes for egress and ingress, light and air. Thus walled in, their position was absolutely impregnable from above or below. It is astonishing in what a limited space these beings contrived to exist; some of these cave-dwellings are scarcely large enough for a man to crawl into.
More pretentious than these are the cliff-houses, which are built in similar situations, differing only in the height of the crevices. Many excellent examples of these have been found. They are generally well preserved, as their situations protect them in great measure from the elements. There are several in the cañon of the Rio Mancos. In one
