As above mentioned the foundations of many walls are of larger stones, and the masonry here is coarser than higher up, which has led some authors to ascribe this fact as due to two epochs of construction. But this conclusion does not appear to be wholly justifiable, although there is evidence in many places that there has been rebuilding over old walls and consequent modification in new constructions, by which older walls have ceased to be necessary, a condition not unlike that existing in several of the Hopi pueblos. In this category may be included the several doors and windows that have been filled in with new masonry or even concealed by new walls. From the fragile character of certain foundations of high walls it would appear that it was not the intention, when they were laid, to erect on them walls more than one story high; the construction of higher stories upon them was an afterthought. Evidences occur of repair of breaks in the walls and corners by the aboriginal occupants, one of the most apparent of which appears at the end of the court in the southern wall of room 59. ADOBE BRICKS The walls, as a rule, were made of stone; indeed it is unusual to find adobe walls in cliff-dwellings of the Mesa Verde. In prehistoric buildings in our Southwest, evidences that the ancients made adobe bricks, sun-dried before laying, are very rare. Bricks made of clay are set in the walls of the Speaker-chief's House and were found in the fallen débris at its base. These bricks were made cubical in form before laying, but there is nothing to prove that they were molded in forms or frames, nor do they have a core of straw as in the case of the adobes used in the construction of Inscription House in the Navaho National Monument, Arizona.[24] The use of adobes in the construction of cliff-house walls has not been previously mentioned, although we find references to "lumps of clay" in the earliest historic times among Pueblos. Thus the inhabitants of Tiguex, according to Castañeda, were acquainted with adobes. "They collect," says this author, "great heaps of thyme and rushes and set them on fire; when the mass is reduced to ashes and charcoal they cast a great quantity of earth and water upon it and mix the whole together. They knead this stuff into round lumps, which they learn to dry and use instead of stone." [Footnote 24: See _Bulletin 50, Bureau of American Ethnology_.] [Illustration: PLATE 12 PHOTOGRAPHED BY R. G. FULLER THE SQUARE TOWER, BEFORE AND AFTER REPAIRING]