The south and east fronts of Casa Grande seem to have suffered,
particularly from the weather, and here rainstorms have probably caused
some of the damage. The outer faces of the walls are of the same
material as the wall mass, all the masonry being composed of earth from
the immediate site. In the construction of the walls this soil was laid
up in successive courses of varying thickness, whose limits form clearly
defined and approximately horizontal joints. The northeast and southeast
corners of the building have entirely fallen away, and low mounds of
their debris still show many knobs and lumps, parts of the original wall
mass.
The destruction of the walls was due mainly to undermining at the ground
level. The character of this undermining is shown in many of the
illustrations to this report, especially in plate CXVI, and its extent
is indicated on the accompanying ground plan (plate CXVII) by dotted
lines within the wall mass. Although the material of which the walls are
composed is very hard when dry, and capable of resisting the destructive
influences to which it has been subjected for a long time, yet under
certain conditions it becomes more yielding. The excessively dry climate
of this region, which in one respect has made the preservation of the
ruin possible, has also furnished, in its periodic sandstorms, a most
efficient agent of destruction. The amount of moisture in the soil is so
small as scarcely to be detected, but what there is in the soil next to
the walls is absorbed by the latter, rising doubtless by capillary
attraction to a height of a foot or more from the ground. This portion
of the wall being then more moist than the remainder, although possibly
only in an infinitesimal degree, is more subject to erosion by flying
sand in the windstorms so frequent in this region, and gradually the
base of the wall is eaten away until the support becomes insufficient
and the wall falls en masse. The plan shows that in some places the
walls have been eaten away at the ground level to a depth of more than a
foot. Portions of the south wall were in a dangerous condition and
likely to fall at any time.
Visiting tourists have done much damage by their vandalism. They have
torn out and carried away every lintel and every particle of visible
wood in the building. After the removal of the lintels a comparatively
short time elapses before the falling in of the wall above. Apparently
but a small amount of this damage can be attributed to rainstorms,
which, although rare in this region, are sometimes violent. There is
evidence that the present height of the walls is nearly the original
height, in other words, that the loss from surface erosion in several
centuries has been trifling, although numerous opinions to the contrary
have been expressed by causal observers. The eastern wall has suffered
more from this cause than the others; a belt on the northern half,
apparently softer than the remainder of the wall, has been eaten away to
a depth of nearly a foot. The interior wall faces are in good condition
generally, except about openings and in places near the top.
Evidences of the original flooring are preserved in several of the
rooms, especially in the north room. The flooring conformed to the
pueblo type in the use of a series of principal beams, about 3 inches in
diameter, above which was a secondary series smaller in size and placed
quite close together, and above this again a layer of rushes with a
coating of clay. All the walls show evidences of the principal series of
beams in the line of holes formed by their ends where they were embedded
in the walls. In the south wall, in parts of the east wall high up on
the level of the upper roof, and in parts of other walls a few stumps of
floor beams remained. These specimens of aboriginal woodwork have
survived only because they are not in sight from the ground, and their
existence therefore was not suspected by the tourists. Evidence of the
other features of the floor construction can be seen on the walls in
places where they have left an imprint, as described in the memoir
previously cited.
No single opening remains intact, as the lintels have been removed from
every one of them. This is particularly unfortunate, for openings at
their best are an element of weakness in a wall, and here each opening,
after the lintel was removed, became, as it were, a center of weakness
from which the destruction of the wall mass gradually proceeded further
and further.