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 not at all or but very little in the desert, by the process of sub- irrigation. There are today healthy stands of scrub along abandoned watercourses and even in the open piedmont where the distance to ground water is only a few feet. A further slight shift or a Jocal diminution of the dratnage discharge {not a diminished rainfall) would end in the destruction of the growths at these precarious sites. Later floods would then bury the stumps and fallen trunks, and we should have the appearance of a forest lost through climatic change. It is not enough to say that a diminished rainfall would produce like effects. The natural processes operating on a desert pied- mont are quite sufficient to produce the visible effects. A new cause need not be sought, and if it is adopted it can only be when contemporary evidence of actual forests of larger size than the local stands of today and of reasonably well known extent, not merely buried fragments, are found. The general theory of climatic change is invitingly simple and spectacular. ] believe that such a change must have occurred in the Puna de Atacama and about its borders. But whether the amount of change was sufficiently great in the human period to be determinable today from the scant evidences left behind by earlier folk is a question that can be settled only by further studies in the field.

Returning to the Puna region, it has been argued that the site of the famous ruin called the Pucaré of Rinconada, about 12 miles south of the village of Rinconada (Fig. 87), was occupied by a compact settlement at a time of heavier rainfall, sufficient to water the andenes, or cultivated terraces, for these are so situated as to be incapable of irrigation today. The fields and the villages were often far apart, as in the case of the pueblos of Arizona and New Mexico. The cultural ele- ments, which include a remarkable colored fresco, besides grinding stones, hatchets, pottery, arrowheads, and the like, are of a type denoting a substantial settlement, while some