HABITATIONS AFFECTED BY ENVIRONMENT. 



479 



shelters of the cliffs were occupied. If predatory border-tribes, tempted 

 by the food-stores of the horticultural farm-house builders, made in- 

 cursions ou the latter, they would find them, scattered as they were, 

 an easy prey. 



ADDED STORIES FOR CLIFF DWELLINGS DEVELOPED FROM LIMI- 

 TATIONS OF CLIFF-HOUSE SITES. 



This condition of things would drive the people to seek security in 

 the neighboring cliffs of fertile canons, where not only might they build 

 their dwelling places in the numerous rock-shelters, but they could also 

 cultivate their crops in comparative safety along the limited tracts 



Fig. 498.— A typical cliff-dwelling. 



which these eyries overlooked. The narrow foothold afforded by many 

 of these elevated cliff- shelves or shelters would force the fugitives to 

 construct house over house ; that is, build a second or upper story 



