56 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. I47 



we failed to identify all the distinctive qualities that have set the 

 Chaco Culture apart, but we did discover a great deal previously 

 unknown about Pueblo Bonito. We learned that it is the architectural 

 product of two unrelated peoples; that the first of these had been 

 in residence long enough for 5 or 6 feet of blown sand to pile up 

 against their homes before the second group arrived and built upon 

 that sand. Source of the domestic water supply at Pueblo Bonito 

 remains a mystery, but we turn with increasing favor toward the 

 Navaho tradition that water could be had with shallow digging almost 

 anywhere in the valley before erosion of the 1850 arroyo. The great 

 natural cistern on the north cliff overlooking Pueblo Bonito was of 

 limited capacity, even if it existed in A.D. 1000. 



We learned that the forests which furnished roofing timbers for 

 Pueblo Bonito flourished when rainfall was more abundant than it is 

 today; that slow-flowing floodwaters following summer rains had 

 spread widely across the valley floor annually depositing enough black 

 alkali to lessen the productivity of village fields before a 12th-century 

 arroyo lowered the water table beyond reach of surface vegetation. 



We learned that each of three Late Bonitian additions to the 

 original settlement had forced the abandonment and destruction of 

 dwellings previously built ; that plans for a fourth and more extensive 

 addition were left incomplete and a substitute adopted. We learned 

 that this substitute was itself abandoned when the Late Bonitians 

 migrated, leaving their Pueblo II co-residents behind in sole pos- 

 session of the compound pueblo. That these original settlers were 

 last to depart is clear from the foodstuffs, the household utensils, 

 and the ceremonial paraphernalia they left in their brush-roofed 

 houses. 



Reduction in arable lands, a consequence of reduced rainfall or 

 erosion, seems a most likely cause for desertion of Chaco Canyon by 

 the Bonitians. The Great Drought of 1276-1299 occurred 100 years 

 too late to have been influential, but that of 1090-1101, perhaps an 

 incentive for Bryan's buried arroyo, could have spurred the outgoing. 



In the chapters which follow I shall seek to present Pueblo Bonito 

 as we now know it, from the original P. II settlement to the last of 

 the three additions planned and executed by the Late Bonitians. 



