although
seen to a limited extent in ruins known to belong to a period subsequent
to the Spanish conquest. Its discovery, therefore, in the Casa Grande
would be important; but no trace of it can be found. The walls are
composed of huge blocks of earth, 3 to 5 feet long, 2 feet high, and 3
to 4 feet thick. These blocks were not molded and placed in situ, but
were manufactured in place. The method adopted was probably the erection
of a framework of canes or light poles, woven with reeds or grass,
forming two parallel surfaces or planes, some 3 or 4 feet apart and
about 5 feet long. Into this open box or trough was rammed clayey earth
obtained from the immediate vicinity and mixed with water to a heavy
paste. When the mass was sufficiently dry, the framework was moved along
the wall and the operation repeated. This is the typical pise or
rammed-earth construction, and in the hands of skilled workmen it
suffices for the construction of quite elaborate buildings. As here
used, however, the appliances were rude and the workmen unskilled. An
inspection of the illustrations herewith, especially of plate LV,
showing the western wall of the ruin, will indicate clearly how this
work was done. The horizontal lines, marking what may be called courses,
are very well defined, and, while the vertical joints are not apparent
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 t