_General use of kivas._--Wherever the remains of pueblo architecture occur among the plateaus of the southwest there appears in every important village throughout all changes of form, due to variations of environment and other causes, the evidence of chambers of exceptional character. The chambers are distinguishable from the typical dwelling rooms by their size and position, and, generally, in ancient examples, by their circular form. This feature of pueblo architecture has survived to the present time, and is prominent in all modern pueblos that have come under the writer’s notice, including the villages of Acoma and Jemez, belonging to the Rio Grande group, as well as in the pueblos under discussion. In all the pueblos that have been examined, both ancient and modern, with the exception of those of Tusayan, these special rooms, used for ceremonial purposes, occupy marginal or semidetached positions in the house clusters. The latter are wholly detached from the houses, as may be seen from the ground plans. _Origin of the name._--Such ceremonial rooms are known usually by the Spanish term “estufa,” meaning literally a stove, and here used in the sense of “sweat house,” but the term is misleading, as it more properly describes the small sweat houses that are used ceremonially by lodge-building Indians, such as the Navajo. At the suggestion of Major Powell the Tusayan word for this everpresent feature of pueblo architecture has been adopted, as being much more appropriate. The word “kiva,” then, will be understood to designate the ceremonial chamber of the pueblo building peoples, ancient and modern.