to approximate, the rate of destruction quantitatively, especially
so since it goes on cumulatively, with constantly increasing
rapidity, as the cemented surfaces are destroyed and the crevices
widen and deepen; but judging from the history of the ruin, and from
the rate of destruction indicated by comparing the photographs of
1892 with the present aspect, it would seem safe to conclude that,
if protected completely from vandalism, the ruin will be
comparatively little injured during the next five years, and will
stand perhaps half a century, without further protective works,
before moldering into dust.

In view of the slow yet ever increasing rate of destruction of the
ruin, and of its great interest as a tangible record of the
prehistoric inhabitants of this country, no hesitation is felt in
recommending that the structure be further protected, and
practically perpetuated, by a suitable roof, so designed as to
shield the walls from rain and sun and at the same time permit an
unobstructed view of the ruin from any direction.
* * * * *
I have the honor to be, sir, yours, with great respect,

J. W. Powell, _Director_.
Secretary of the Interior.




INDEX