It will be seen, therefore, that it is impossible to base any chronologic conclusions on the presence or absence of this feature, notwithstanding the undoubted priority of the circular form, except in so far as these conclusions are limited to some certain region or known tribal stock. If it be assumed that the Verde ruins belong to the Tusayan, and all the evidence in hand favors that assumption, the conclusion follows that they should be assigned to a comparatively late period in the history of that tribe. That the period of occupancy of the lower Verde valley was not a long one is proved by the character of the remains and by what we know of the history of the pueblo-building tribes. There are no very large areas of tillable land on the lower Verde and not a large number of small ones, and aside from these areas the country is arid and forbidding in the extreme. Such a country would be occupied only as a last resort, or temporarily during the course of a migration. The term migration, however, must not be taken in the sense in which it has been applied to European stocks, a movement of people en masse or in several large groups. Migration as used here, and as it generally applies to the Pueblo Indians, means a slow gradual movement, generally without any definite and ultimate end in view. A small section of a village, generally a gens or a subgens, moves away from the parent village, perhaps only a few miles. At another time another section moves to another site, at still another time another section moves, and so on. These movements are not possible where outside hostile pressure is strong, and if such pressure is long continued it results in a reaggregation of the various scattered settlements into one large village. Such in brief is the process which is termed migration, and which has covered the southwest with thousands of village ruins. Of course larger movements have occurred and whole villages have been abandoned in a day, but as a rule the abandonment of villages was a gradual process often consuming years. [Illustration: Plate XLVIII. MASONRY OF RUIN AT MOUTH OF THE EAST VERDE.] Before the archeologic investigation of the pueblo region commenced and when there was little knowledge extant by which travelers could check their conclusions, the immense number of ruins in that region was commonly attributed to an immense population, some writers placing the number as high as 500,000. Beside this figure the present population, about 9,000, is so insignificant that it is hardly surprising that the ancient and modern villages were separated and attributed to different tribal stocks.