very significant.
Although as yet our knowledge of the cliff houses of the upper Gila
and Salado and their numerous tributaries is very fragmentary, and
generalization on that account unsafe, it may be stated provisionally
that no circular kivas have yet been found in any ruins of the
Gila-Salado watershed. This form of kiva, however, is an essential
feature of the cliff dwellings of Rio Colorado, especially of those
along its affluents in southern Colorado and northern New Mexico.
Roughly speaking, then, the circular kiva is characteristic of the
ruins of this region and of certain others in the valley of the Rio
Grande, where they still survive in inhabited pueblos.

Circular ruins likewise are limited in their distribution in the
Southwest, and it is an interesting fact that the geographic
distribution of ancient pueblos of this form is in a general way the
same as that of circular kivas. There are, of course, many exceptions,
but so far as I know these can readily be explained. No ruins of
circular dwellings occur in the Gila-Salado drainage area, where
likewise no circular kivas have been observed. Moreover, the circular
form of dwelling and kiva is distinctively characteristic of
prehistoric peoples east of Tusayan, and the few instances of their
occurrence on its eastern border can readily be explained as
extra-Hopi.

The explanation of these circular kivas advanced by Nordenskioeld and
the Mindeleffs, that they are survivals of round habitations of
nomads, has much to commend it; but whether sufficient or not, the
geographic limitation of these structures tells in favor of the
absence of any considerable migration of the prehistoric peoples of
the upper Colorado and Rio Grande watersheds southward into the
drainage area of the Gila-Salado. Had the migration been in that
direction it may readily be believed that the round kiva and the
circular form of dwelling would have been brought with it.

The round kiva has been regarded as a survival of the form of the
original homes of the nomad, when he became a sedentary agriculturist
by conquest and marriage.

The presence of rectangular kivas in the same areas in which round
kivas occur does not necessarily militate against this theory, nor
does it oblige us to offer an explanation of a necessarily radical
change in architecture if we would derive it from a circular form. It
would indeed be very unusual to find such a change in a structure
devoted to religious pu