HENDERSON 



GEOLOGY AND TOPOGRAPHY 35 



The use of tufa in the construction of the walls of buildings is a 

 natural outgrowth of environment. Adobe earth and other conve- 

 nient building materials are absent from the canyons and mesas 

 of this district, while tufa is abundant, light, easily handled, and 

 readily worked. 



Water was furnished to the ancient inhabitants by El Rito de los 

 Frijoles, a small rivulet across which one may easily step at almost 

 any point during ordinary stages. The stream has its source in the 

 Jemez mountains. Its volume responds very readily to meteorolog- 

 ical conditions there. Twice during the summer of 1910, after a few 

 days A\dthout rain in the mountains, the water almost ceased to flow 

 for a few hours, and throughout August long stretches of the channel 

 below the open valley were dry, only a tiny rill flowing over the falls. 

 So far as present knowledge goes, desiccation would not account 

 for the total abandonment of this valley, though it might account 

 for a reduction of the population. It would support at present a 

 small clan. The creek is so near the point of extinction, however, 

 that it is altogether probable that durmg some of the dryer cycles it 

 dries up entirely for a year or series of years. Indeed, the reported 

 disappearance of trout, discussed in the zoologic report in prepara- 

 tion as Bulletin 56 of this series, strongly suggests such a drought 

 within the last 20 years. The notable scarcity or absence of algae, 

 aquatic insect larvae, and aquatic mollusks suggests the same thing. 

 As no one has continuously resided there for any great length of 

 time, definite information on this interesting phase of the subject is 

 not yet obtainable. A few aquatic beetles were noted. 



Returnmg now to the cliff on the north side of the canyon, whose 

 archeologic importance has been mentioned, it is fountl to be the 

 dominant feature of the landscape, which must at once impress every 

 observer. At the base of the cliff are many artificial caves, con- 

 nected to some extent with one another. They once formed rear 

 rooms of dwellings, one to three or four stories m height, which were 

 erected in front of them and the walls of which have long since fallen 

 in. Everywhere much smaller ca\aties occur in the face of the cliff. 

 If the artificial caves were not formed by enlarging some of the larger 

 natural cavities, at least the idea of cave rooms was probably sug- 

 gested by Nature's handiwork. The tufa composing the cliff can 

 be easily excavated with the rude stone, bone, and wooden tools of 

 the ancient workmen. Fortunately the cliff faces southward, so that 

 the houses would be warm and dry in winter. The cave rooms 

 also are perfectly dry, a condition which might not have obtained 

 if they were on the south side of the canyon, where evaporation is 

 less and some snow lies on the rocks for weeks at a time. 



Below the caves and dwellings is a steep talus slope extending out 

 into the valley. Above the top of the main cliff are several terraces 



