in the illustration, a close inspection of the wall itself shows them.
It will be noticed that the builders were unable to keep straight
courses, and that occasional thin courses were put in to bring the wall
up to a general level. This is even more noticeable in other parts of
the ruin. It is probable that as the walls rose the exterior surface was
smoothed with the hand or with some suitable implement, but it was not
carefully finished like the interior, nor was it treated like the latter
with a specially prepared material. The material employed for the walls
was admirably suited for the purpose, being when dry almost as hard as
sandstone and practically indestructible. The manner in which such walls
disintegrate under atmospheric influences has already been set forth in
detail in this report. An inhabited structure with walls like these
would last indefinitely, provided occupancy continued and a few slight
repairs, which would accompany occupancy, were made at the conclusion of
each rainy season. When abandoned, however, sapping at the ground level
would commence, and would in time level all the walls; yet in the two
centuries which have elapsed since Padre Kino's visit--and the Casa
Grande was then a ruin--there has been but little destruction, the
damage done by relic hunters in the last twenty years being in fact much
greater than that wrought by the elements in the preceding two
centuries. The relic hunters seem to have had a craze for wood, as the
lintels of openings and even the stumps of floor joists have been torn
out and carried away. The writer has been reliably informed that as late
as twenty years ago a portion of the floor or roof in one of the rooms
was still in place, but at the present day nothing is left of the floors
except marks on the vertical walls, and a few stumps of floor joists,
deeply imbedded in the walls, and so high that they can not be seen from
the ground.

[Illustration: Pl. LVI: Interior Wall of Casa Grande Ruin.]