Linguistic researches have shown the close connection which exists between the Hopi (Moki) and some of the plains (or so called "wild") Indians. There is no doubt that at the time of the Spanish discovery, some three hundred and fifty years ago, the Hopi were quite as far advanced as the other pueblo tribes, and the conclusion is irresistible that since it may reasonably be inferred that one tribe has made the change from a nomadic to a sedentary life, other tribes also may have done so. We may go even farther than this, and assume that a nomadic tribe driven into the pueblo country, or drifting into it, would remain as before under the direct influence of its physical environment, although the environment would be a new one. Granting this, and the element of time, and we will have no difficulty with the origin of pueblo architecture. The complete adaptation of pueblo architecture to the country in which it is found has been commented on. Ordinarily such adaptation would imply two things--origin within the country, and a long period of time for development--but there are several factors that must be taken into consideration. If the architecture did not originate in the country where it is found it would almost certainly bear, traces of former conditions. Such survivals are common in all arts, and instances of it are so common in architecture that no examples need be cited. Only one of these survivals has been found in pueblo architecture, but that one is very instructive; it is the presence of circular chambers in groups of rectangular rooms, which occur in certain regions. These chambers are called estufas or kivas and are the council houses and temples of the people, in which the governmental and religious affairs of the tribe are transacted. It is owing to their religious connection that the form has been preserved to the present day, carrying with it the record of the time when the people lived in round chambers or huts,