Casa Grande Ruin | Page 6

were nearly filled up would the pronounced disintegration of the
outer walls of the structures commence. At that period the walls were
probably covered and protected by debris dropping from above, and
possibly the profile of the mounds was already established, being only
slightly modified by surface erosion since.

[Illustration: Pl. LII: Ground Plan of Casa Grande Ruin.]
About the center of the eastern side of the terrace, and also on the
western side, the water which falls on the surface of the structure is
discharged through rather pronounced depressions at these points.
These depressions are not the work of running water, though doubtless
emphasized by that agency, but represent low or open spaces in the
original structure, probably passageways or gateways. Furthermore,
before or inside each gateway there is a slightly depressed area, just
where we would expect to find it under our hypothesis, and showing
that the process of filling in is not yet completed. If the structure were
to remain undisturbed for some decades longer these spaces would
doubtless be filled up from material washed from the mounds, giving
eventually a continuous slope from the base of the mounds to the edge
of the terrace.
On the eastern margin of the map and in the southeastern corner two
small and sharply defined mounds, differing in character from any
others of the group, are represented. That shown on the eastern margin
rises about 6 feet and the other about 10 feet above the surrounding
level, and both stand out alone, no other remains occurring within a
hundred yards in any direction. These mounds seem a thing apart from
the other remains in the group; and it is probable that they represent the
latest period in the occupancy of this site, or possibly a period
subsequent to its final abandonment as a place of residence. Analogous
remains occur in conjunction with some large ruins in the north, and
there they represent single rooms, parts of the original structure kept in
a fair state of preservation by occasional repairs while the remainder of
the village was going to ruin, and used as farming outlooks long after
the site was abandoned as a place of residence. As these farming
outlooks have been discussed at some length in another paper[1] it is
not necessary here to enlarge upon their function and the important part
they play in Pueblo architecture. If the high mounds in question mark,
as supposed, the sites of farming outlooks such as those which are
found in the north, they indicate that the occupancy of the region in
which they occur was continued after the abandonment of the Casa
Grande structure by the people who built it or by people of similar

habits and customs.
[Footnote 1: A Study of Pueblo Architecture; 8th Ann. Rep. Bur. Eth.,
1891, pp. 86, 227, and elsewhere.]
An inspection of the map will show a number of depressions, some of
quite large area, indicated by dotted contour lines. The principal one
occurs a little west of the center of the area, and is worth more than a
passing notice since similar structures are widely distributed throughout
this region. It may be roughly characterized as a mound with excavated
center. The ground for some distance about the structure (except for
two depressions discussed later) is quite flat. From this flat surface as a
base the structure rises to a height of 5 feet. From the exterior it has the
appearance of an ordinary mound, but on reaching the top the interior is
found to be hollowed out to a depth which even at the present day is
below the surrounding surface, although not below the depressions
adjoining. The main structure or mound is shown in figure 329 (an
enlargement from the map). It measures on top of the crest 150 feet
from north to south and about 80 feet from east to west, but covers a
ground area of 200 feet by 120 feet or over half an acre. The crest is of
the same height throughout, except for slight elevations on the eastern
and western sides and a little knoll or swell in the southwestern corner.
There is no indication of any break in the continuity of the crest such as
would be found were there openings or gateways to the interior. The
bottom of the depression in the main structure is at present about a foot
below the surrounding ground surface, but it must have been originally
considerably more than this, as the profile indicates long exposure to
atmospheric erosion and consequent filling of the interior. No
excavation was made and the character of the construction can not be
determined, but the mound is apparently a simple earth structure--not
laid up in blocks, like the Casa Grande ruin.
[Illustration: Fig. 329.--Map of hollow mound.]