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,