The cliff ruins have always been regarded as defensive structures, sometimes even as fortresses, but in De Chelly whatever value they have in this respect is due solely to the sites they occupy. There are many places here where slight defensive works on the approaches to sites would increase their value a hundredfold, but such works were apparently never constructed. Furthermore, the ruins themselves never show even a suggestion of the influence of the defensive motive, except in the two possible instances already mentioned. The ordinary or dwelling-house plan has not been at all modified, not even to the extent that it has in the modern pueblos. If the cliff ruins were defensive structures it would certainly seem that an influence strong enough to bring about the occupancy of such inconvenient and unsuitable sites would also be strong enough to bring about some modifications in the architecture, modifications which would render more suitable sites available. The influence of the physical environment on pueblo architecture, and the sensitiveness of the latter to such influence, has already been commented on. Moreover, it also has been stated that, so far as known, but one instance occurs in the canyon where provision was made for the storage of water; yet without water the strongest "fortress" in the canyon could not withstand a siege of forty-eight hours. Further, assuming that the structures were defensive, and well prepared to resist attack, if necessary, for several days, only a few such attacks would be required to cause their abandonment, for the crops on the canyon bottom, practically the sole possessions of the dwellers in the canyon, would necessarily be lost. [Illustration: Plate LXII Navaho Burial Cists] These are some of the difficulties that stand in the way of the assumption that the cliff ruins were defensive structures or permanent homes. If, however, we adopt the hypothesis that they were farming outlooks occupied only during the farming season, and then only for a few days or weeks at a time, after the manner that such outlooks are used by the Pueblo Indians at the present time, most of the difficulties vanish.