In ruin 31 there is another example. The kiva here was about 20 feet in diameter, with rather thin walls smoothly plastered inside. On the inner side the walls are from 3 to 5 feet high; outside they are generally flush with the ground. The kiva is not a true circle, but is slightly elongated north and south. On the south side, nearest the edge of the ledge, there is an opening, shown in figure 70. The opening is 6 feet 3 inches wide, and the ends of the curved walls terminate in smoothly finished surfaces. In front of it there are remains of two walls, about a foot apart, and so arranged as to form an apparent passageway into the interior of the kiva. These seem to be a kind of platform, like that just described, but close inspection shows the walls, which can be traced to within 6 inches of the inner wall of the kiva. This also may be the remains of a chimney-like structure. There are other points in the canyon where the same feature occurs, but in none of them is the evidence of an opening or doorway more definite than in the examples described. [Illustration: Fig. 71--Plan of part of a kiva in ruin No. 10.] The masonry of the kivas is always as good as that of any other structure on the site, and generally much better. The walls are usually massive; sometimes they are 3 feet thick in the upper part and 4 feet in the lower portion, where the bench occurs. In a few cases the kiva has an upper or second story, but when this occurs no attempt is made to preserve the circular form, and the upper rooms are really rectangular with much rounded corners. Plate XLIX shows a second-story kiva wall in Mummy Cave ruin, and plate LXIII one in ruin No. 10 in De Chelly. The latter occurs over the principal kiva, and the walls which are still standing on the north and west sides are approximately straight, but the corners are much rounded. Figure 71 is a detailed plan of part of the kiva, showing the arrangement of the upper walls. The kiva walls are about 18 inches thick. On the north side the upper wall is supported by a heavy beam, part of which is still in place. Under the north-east corner of the upper room there is a little triangular space formed by a short connecting wall, shown on the plan. This is really a flying wall, covering only the upper portion of the space, and its purpose is not clear, as the opening left is not large enough to permit the passage of a person, and was available only from the second story.