The opening immediately below the last described is filled with debris to the level of the lintel. Above this, however, there is a series of three tiers of sticks with 6 to 8 inches of masonry between them vertically, sometimes laid side by side, sometimes separated by a foot of masonry. Some of these lintel poles, as well as those of the opening above it, extend 3 feet into the wall, others only a few inches. The lower sides or bottoms of the holes are washed with pink clay, the same material used for surfacing the interior walls. Perhaps this was merely the wetting used to make succeeding courses of clay stick better. This opening is shown in plate LIX. Near the middle of the northern wall there are two openings, one above the other. The upper opening was finished in the same manner as those already described. But two tiers of poles show above it, though the top is well preserved, and another tier may be buried in the wall. There are indications that the opening was closed by a block about 2 feet thick and flush with the outside. The height of the opening was 4 feet 5 inches, width at top 1 foot 41/2 inches, and at the bottom 1 foot 10 inches. It narrows a little from north to south. The lower opening is so much broken out that little remains to show its character. There is a suggestion that the opening was only 2 feet high, and there were probably three tiers of lintels above the opening, the top of which was 21/2 feet below the roof beams, but the evidence is not so clear as in the other instances. In the middle of the western wall, at a height of 5 feet 8 inches above the first roof level, there is a large, roughly circular opening or window, 14 inches in diameter. This is shown in plate LX. It is smoothly finished, and enlarges, slightly, outward. CONCLUSIONS. As before stated, any conclusions drawn from a study of the Casa Grande itself, and not checked by examination of other similar or analogous ruins, can not be considered as firmly established, yet they have a suggestive value. From the character of the remains it seems probable that the site of the ruins here designated as the Casa Grande group was occupied a long time, not as a whole, but piecemeal as it were, one part being occupied and abandoned while some other part was being built up, and that this ebb and flow of population through many generations reached its final period in the occupation of the structure here termed the Casa Grande ruin. It is probable that this structure did not exist at the time the site was first occupied, and still more probable that all or nearly all the other sites were abandoned for some time before the structure now called the Casa Grande was erected. It is also probable that after the abandonment of the Casa Grande the ground about it was still worked by its former population, who temporarily occupied, during the horticultural season, farming outlooks located near it. [Illustration: Pl. LX: Circular Opening in North Room.]