All these
peoples were at least one full ethnical period nearer to true
civilization than the Iroquois,--and a vast amount of change and
improvement is involved in the conception of an entire ethnical period.
According to Mr. Morgan, one more such period would have brought the
average level of these Cordilleran peoples to as high a plane as that of
the Greeks described in the Odyssey. Let us now observe the principal
points involved in the change, bearing in mind that it implies a
considerable lapse of time. While the date 1325, at which the city of
Mexico was founded, is the earliest date in the history of that country
which can be regarded as securely established, it was preceded by a long
series of generations of migration and warfare, the confused and
fragmentary record of which historians have tried--hitherto with scant
success--to unravel. To develop such a culture as that of the Aztecs out
of an antecedent culture similar to that of the Iroquois must of course
have taken a long time.

[Sidenote: Horticulture with irrigation, and architecture with adobe.]

It will be remembered that the most conspicuous distinctive marks of the
grade of culture attained by the Cordilleran peoples were two,--the
cultivation of maize in large quantities by irrigation, and the use of
adobe-brick or stone in building. Probably there was at first, to some
extent, a causal connection between the former and the latter. The
region of the Moqui-Zuni culture is a region in which arid plains become
richly fertile when water from neighbouring cliffs or peaks is
directed down upon them. It is mainly an affair of sluices, not of pump
or well, which seem to have been alike beyond the ken of aboriginal
Americans of whatever grade. The change of occupation involved in
raising large crops of corn by the aid of sluices would facilitate an
increase in density of population, and would encourage a preference for
agricultural over predatory life. Such changes would be likely to favour
the development of defensive military art. The Mohawk's surest defence
lay in the terror which his prowess created hundreds of miles away. One
can easily see how the forefathers of our Moquis and Zunis may have come
to prefer the security gained by living more closely together and
building impregnable fortresses.

[Sidenote: Possible origin of adobe architecture.]

The earthen wall of the Mandan, supported on a framework of posts and
slabs, seems to me curiously and st