404 SMITHSOXIAX MISCELLANEOUS COLLECTIONS VOL. 52 



to embrace the more important clusters of the Casa Grande type in 

 the valleys under consideration. Small mounds^ with fragments of 

 pottery or broken metates indicative of habitations are scattered over 

 the plain in every place in the desert where irrigation was possible. 

 Their number and distribution indicate a considerable population, 

 often settled at some distance from the great dwellings, but gener- 

 ally near remnants of the prehistoric irrigation ditches that one con- 

 stantly encounters in these regions. 



The level plains bordering the Gila River and its tributaries were 

 inhabited in prehistoric times by an agricultural people having a 

 homogeneous culture. The prehistoric inhabitants built houses of 

 two types : the one large, often several stories high, with massive 

 walls, and the other, of more fragile character, serving for their 

 dwellings. The material with which the latter were built and the 

 manner in which they were constructed were not sufficiently durable 

 to resist the elements, and the walls have fallen, augmenting the 

 height of the debris accumulated at their foundations. Sand blown 

 by winds has drifted over the ruins, covering the rooms and forming 

 mounds over them, from which, in a few cases, there still project, 

 a few feet high, irregular fragments of the original walls. 



When the Gila A'alley was first visited by the Spanish explorers 

 the projecting walls of these buildings were more plainly visible than 

 at present and their true character and architecture were more ap- 

 parent. It was at that time easier to recognize the characteristic 

 type of structure of the buildings to which they belonged, for the 

 walls are now almost completely buried. The massive walled build- 

 ings in these plains were early called Casas Grandes, or Great 

 Houses,- one of the best of which, the historic Casa Grande, still 

 preserves the ancient type. A knowledge of these houses, derived 

 from laying bare the walls by excavations, shows that in their form 

 and construction they are characteristic. They differ radically from 

 clifif dwellings, pueblos, or those other prehistoric constructions in 

 our Southwest/ with which, however, they have certain affinities. 



' Many artificial mounds in the Gila Valley show no indication of walls. 

 Among these may be mentioned those formed of refuse or trash heaps and 

 accumulations of earth incidentally thrown up in digging reservoirs or irriga- 

 tion ditches. The sites of "mescal pits" or depressions in the earth where 

 mescal was formerly roasted are indicated by earth much darker than that of 

 the surrounding plain. 



" The words "Casas Grandes" and Great Houses are used as synonyms of 

 compounds. 



^ The four types of prehistoric dwellings in the Southwest may be known as; 

 (i) cavate habitations; (2) cliff dwellings; (3) pueblos; (4) compounds. 

 The essential difference between (i) and (2) is that the former are dug out 



