estufa applies in every respect to the second, with the single exception that the whole wall is coated with yellow plaster without any red painting. The wall between the hearth and the singular passage or tunnel described above is replaced by a large slab of stone set on end. It is difficult to say for what purpose this tunnel has been constructed and the slab of stone or the wall erected in front of it. As I have mentioned above, this arrangement is found in all the estufas.[25] [Footnote 24: In the ground plan given there is no point shown where the walls of the kiva touch adjoining rooms.] [Footnote 25: Cliff Dwellers of the Mesa Verde, pp. 15-17, figs. 6 and 7.] The general similarity between the kivas of De Chelly and those of the Mesa Verde region will be apparent from the above description. It should be added that in the section which accompanies it the roof of the tunnel appears to be supported by a series of small cross sticks, although no information on this point is afforded by the test. The examples which occur in De Chelly are apparently much ruder and more primitive than those of the Mancos, and only one of them approaches the latter in finish and elaboration. In another place[26] Nordenskioeld mentions an example in which two small sticks were incorporated in the masonry of the upper part of the tunnel in a diagonal position. From this he rejects Holmes' explanation that the passageway was used as an entrance to the kiva, nor does he find the chimney hypothesis satisfactory. He states, further, that the use of this feature as a ventilator seems highly improbable. In one place he found the curtain or screen constructed not of masonry, but-- ... of thick stakes, driven into the ground close to each other, and fastened together at the top with osiers. On the side nearest to the hearth this wooden screen was covered with a thick layer of mortar, probably to protect the timber from the heat.[27] [Footnote 26: Loc. cit., p. 32.] [Footnote 27: Loc. cit., p. 70.] As stated elsewhere, the first hypothesis formed in the field as to the purpose of these chimney-like structures was that they were abortive chimneys, but this was found untenable. The next hypothesis, formed also in the field, was that they were ceremonial in origin and use, but why they should connect with the open air is not clear. If we could assume that they were ventilators, the problem would be solved, but it is a far cry from pueblo architecture to ventilation; a stride, as it were, over many centuries. Ventilation according to this method--the introduction of fresh air on a low level, striking on a screen a little distance from the inlet and being thereby evenly distributed over the whole chamber--is a development in house architecture reached only by our own civilization within the last few decades.