MmoELEFF] EXTENT OF CASA GRANDE GROUP. 299 



by well deflued remains, as tbere shown, extends about 1,800 feet north 

 and south and 1 ,500 feet east and west, or a total area of about 65 

 acres. 



The Casa Grande ruin, as the term is here used, occupies a position 

 near the southwestern corner of the group, and it will be noticed that 

 its size is iiisiguiflcaut as compared with that of the entire group, or 

 even with the large structure in the north-central part of it. The 

 division of the group into northern and southern portions, which has 

 been made by some writers, is clearly shown on the map; but this 

 division is more apparent than real. The contour interval on the map 

 is one foot — a sufficiently small interval to show the surface configura- 

 tion closely and to bring out some of its peculiarities. Depressions are 

 shown by dotted contours. It will be noticed that while most of the 

 mounds which mark the sites of former structures rise but 10 feet or 

 less above the surrounding level, the profiles vary considerably, some 

 being much more smoothed off and rounded than others, the former 

 being shown on the map by even, "flowing" contours, while the latter 

 are more irregular; and it will be further noticed that the irregularity 

 reaches its maximum in the vicinity of the Casa Grande ruin proper, 

 where the ground surface was more recently formed, from the fall of 

 walls tliat wei'e standing within tlie historical period. 



External appearance is a very unsafe criterion of age, although in 

 some cases, like the present, it aflords a fair basis for hypothesis as to 

 comparative age; but even in this case, where the various portions of 

 the group have presumably been affected alike by climatic and other 

 influences, such hypothesis, while perhaps interesting, must be used 

 with the greatest caution. Within a few miles of this place the writer 

 has seen the remains of a modern adobe house whose maximum age 

 could not exceed a decade or two, yet which presented an appearance 

 of antiquity quite as great as that of the wall remains east and south- 

 east of the Casa Grande ruin. 



The application of the hypothesis to the map brings out some interest- 

 ing results. In the first place, it may be seen that in the lowest mounds, 

 such as those in the northwestern corner of the sheet, on the southern 

 margin, and southwest of the well-marked mound on the eastern mar- 

 gin, the contours are more flowing and the slopes more gentle than in 

 others. This suggests that these smoothed mounds are older than the 

 others, and, further, that their i^reseut height is not so great as their 

 former height; and again, under this hypothesis, it suggests that the 

 remains do not belong to one period, but that the interval which 

 elapsed between the abandonment of the structures whose sites are 

 marked by the low mounds and the most recent abandonment was 

 long. In other words, this group, under the hypothesis, attbrds another 

 illustration of a fact constantly impressed on the student of southwest- 

 ern village remains, that each village site marks but an epoch in the his- 

 tory of the tribe occupying it — a period during which there was constant, 



