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SMITHSONIAN MISCELLANEOUS COLLECTIONS 



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historic farms, one source of moisture being now, as in prehistoric 

 times, melting snows. Absence of snow and rain for several con- 

 secutive years might have reduced their crops and starved the aborig- 

 inal dry farmers, even though a permanent change of climate did 

 not occur. 



To utilize their limited water supply the aborigines constructed 

 many reservoirs near their farms to retain snow and rain. These are 

 now indicated by sloping rock surfaces, bare of soil but girt with 



Fig. 137. — Prehistoric reservoir, near Hovenweep Ruins. 

 Photograph by T. G. Lemmon. 



vegetation ; about the lower edge the natives constructed a low 

 bank of earth to serve as a retaining wall. It is estimated that one 

 of these reservoirs (fig. 137) covers a surface of 4 acres; others 

 are still used by herdsmen, who have somewhat increased the height 

 of the retaining walls, for watering stock. 



We find near ruins in this region many examples of enclosures 

 made with slabs of stone set on edge. The use of these structures 

 has not been satisfactorily explained ; they have been variously inter- 

 preted as graves, crematory cists, and storage places or pits for 



