82 THE CLIMATIC FACTOR AS ILLUSTRATED IN ARID AMERICA. 



Before leaving the Chaco Canyon a word should be added as to the succession of 

 races in this region. The small villages or hamlets located upon the plateau at a distance 

 from the main valleys seem to have belonged to a people different from those who later 

 built the large villages, which, however, frequently contain evidences of an occupation 

 previous to that whose remains are now chiefly in evidence. For instance, at Pueblo 

 Bonita, Pepper (who excavated for the American Museum of Natural History in New 

 York) found evidences of an older occupation 10 feet below the one which we have been 

 discussing, and there is a possibility of an intermediate occupation. Three feet under 

 the level of the main plain i^pon which stand the ruins of Pueblo del Arroyo traces of old 

 walls can be seen extending 100 feet beyond the present ruins; the lowest part of these 

 walls is 5 feet below the present surface. At the httle ruin opposite Pueblo Bonita some 

 of the walls extend downward 3 feet lower than the others, suggesting that old walls had 

 fallen into ruins and were then built upon once more after 3 feet of material had accumu- 

 lated. Elsewhere, at points farther up the canyon, old walls are said to lie 12 feet below 

 the present surface. The material in which all these walls are imbedded seems to be the 

 ordinary silts of the valley floor. Without further study no positive conclusions can be 

 based upon them, but they are suggestive. Apparently the Chaco Valley was occupied 

 at least twice. Possibly, although this is pure surmise, the first occupation was at the 

 time when the remoter ruins of the small type were also inhabited. Then the place was 

 abandoned, wholly or in part, and the river deposited from 3 to 12 feet of silt before the 

 next occupation took place. Such deposition, as we have seen, would normally occur in 

 a time of unusual aridity, and hence may be of significance in our chmatic problem. 



The final abandonment of the ruins may also throw light on physical conditions. 

 We have already seen that at the end of the period of the main occupation of the ruins 

 the inhabitants were in straits not only to get water enough, as is clear from their many 

 dams and little reservoirs, but also because of enemies, as appears from the defensive 

 walls and from the way in which in neighboring regions the villagers often took refuge in 

 inaccessible spots upon high hilltops or in deep canyons. An examination of the rooms 

 seems to indicate that the population dwindled gradually. Many rooms are found sealed 

 up, or full of rubbish, showing that for a long time before their final abandonment they were 

 not in use. All these things are exactly what would be expected if the cUmate had become 

 drier. They can also, to be sure, be explained equally well upon various other suppositions, 

 such as the incursion of enemies, or of new people with new ideas, the ravages of disease, 

 the superstitious fear of rooms in which a death has occurred, and other similar theories. 

 These might be given the preference were it not for the evidence wliich we shall present 

 later when we come to discuss the measurements of trees. Meanwhile it is merely necessary 

 to call attention to them. 



One other matter also comes up in this connection: The region of which the Chaco 

 Canyon may be considered typical appears once to have been densely populated, but is 

 now one of the least habitable places in the United States. When the Spaniards arrived in 

 America the ancient inhabitants appear already to have vanished, since no mention is made 

 of them in Spanish chronicles. Moreover, their pottery and methods of architecture were 

 different from those of any tribe of Indians which existed in later times. The fact that 

 the people had vanished proves nothing, but it is interesting to note that it is exactly what 

 we should expect if they were driven out by aridity. Here where the country is excep- 

 tionally dry they would disappear sooner than in better-watered regions, such as the Rio 

 Grande Valley, where the Pueblo Indians had their chief center. We shall return to this 

 general subject later and its bearing will be more fully apparent. 



One of the best places for the study of the relation between older and younger ruins 

 is the Pajaritan Plateau, 20 to 30 miles northwest of Santa Fe. I had the good fortune 

 to be conducted to this region by Mr. Kenneth M. Chapman, the assistant director of 



