g walls. Rayburn was even more astonished than I was
by the exactness with which these great semicircles were laid off; for
he apprehended, as I did not, the difficulty attendant upon running a
line in a true and regular curve. But I am not prepared to say that this
work could not have been accomplished by mere rule of thumb. My friend
Bandelier, in the course of his admirable analysis of the ruins at
Mitla, has made clear to me how easy it is to attribute to scientific
knowledge work that is the result only of manual skill. As I have
pointed out in my discussion of this matter in my _Pre-Columbian
Conditions on the Continent of North America_, the plateau at the top of
this range of terraces easily might have been laid off in a true
semicircle by the simple means of a pointed stick at the end of a long
rope; and from the true line thus established the line of the terrace
below it could have been had--and so on down to the lowest terrace of
all.

There could be no doubt, however, that engineering skill of a high
order--howsoever crude might have been the actual method of its
application--was exhibited both in the preparation of the site, and then
in the city's building. On the site alone an almost incredible amount of
labor had been expended; for the rocky promontory--that primitively, as
the result showed, had been broken and irregular--had been so cut away
in some places, and so filled in in others, and the whole of it had been
so carefully trimmed and smoothed, that in the end it became a huge mass
of rock-work, in the regularity of which there was not perceptible the
smallest flaw. And in this preliminary work, as well as in the building
of the houses afterwards, fragments of stone were used of such enormous
size that the moving of them, Rayburn declared, would be wellnigh
impossible even with the most powerful engineering appliances of our own
time. Nor was the use of these huge pieces of stone confined to the
foundations of the houses. Some of them were high above the ground;
indeed, the very largest that we observed--the weight of which Rayburn
estimated at not less than twenty tons--was a single block that made the
entire top course of a high wall.

All of the stone-work was well smoothed and squared; and while the
exteriors of the houses were entirely plain, we could see through the
open door-ways that the interiors of many of them were enriched with
carvings. All were destitute of windows opening upon the str