The inner surface of the rectangular inclosing wall is marked by a line in the interior of the tunnel. Inside of this line, toward the center of the kiva, the stones composing the wall are large; outside of it they are small. The interior plastering of the kiva is not smoke-blackened, but the coat next the surface is stained, as is also the third coat underneath. The interior of the tunnel is not much smoke-blackened, but it appears probable that part of its roof fell while the structure was still in use, as there are a number of little cavities in the masonry above its roof level filled with soot. A similar effect might result from leaks or cavities between the flat roofing stones. In excavating the tunnel a number of large lumps of clay were found in it, and there is no doubt that they formed part of the roof. Some of these had considerable quantities of grass mixed into them or stuck to the clay on one side. Apparently dry grass was used in the construction. A large fire could not have been built within the tunnel. [Illustration: Fig. 80--Plan of chimney-like structure in ruin No. 16.] The principal kiva in Mummy Cave ruin has an elaborate structure of the kind under discussion. Figure 82 shows a plan of this kiva, of which a general view has already been given (figure 75). The bench extended only partly around the interior, which had a continuous surface at the floor level, except on the southwest. At this point it is interrupted to give place to an elaborate chimney-like structure. Figure 83 is a general view. The wall surface on the southern side of the kiva has been extended inward, as shown on the plan by a lighter shaded area. This was done at some period subsequent to the completion of the kiva, but whether it had any connection with the chimney-like structure could not be determined. The curtain or screen before the opening, which seems to be an invariable feature, is shown in both figures. In this example the tunnel does not pass through the masonry as in those previously described, but occurs in the form of a covered trough, shown in the illustration with the covering removed. It occupies the middle third of a large recess in the main wall of the kiva, and is connected at its outer end with a vertical square shaft about a foot wide. This shaft is separated from the recess above the bench level by a wall only a few inches thick, composed of a single layer of stones. That portion of it which is above the tunnel is supported by a single round stick of wood, as shown in figure 83. The south or inner opening of the tunnel is reduced to two-thirds, of the width elsewhere by a framing composed of bundles of sticks bound together with withes and heavily coated with mud mortar. This was not placed flush with the inner face, but a few inches back, and the whole structure gives an effect of unusual neatness and good workmanship. [Illustration: Fig. 81--Section of chimney-like structure in ruin No. 16]