en move the village. This
was apparently the reason why the Iroquois, although successful in other
ways, failed to establish permanent towns like those of the Pueblos and
the Haidas. Their advancement not only in architecture but in many of
the most important elements of civilization was for this reason greatly
delayed. There was little to stimulate them to improve the land to which
they were attached, for they knew that soon they would have to move.

Farther south the character of the grassy vegetation changes, and the
condition of agriculture alters with it. The grass ceases to have that
thick, close, turfy quality which we admire so much in the fields of the
north, and it begins to grow in bunches. Often a southern hillside may
appear from a distance to be as densely covered with grass as a New
England hayfield. On closer examination, however, the growth is seen
to consist of individual bunches which can easily be pulled up, so that
among the southern tribes the fields did not become filled with grass as
they did in the north, for the women had relatively little difficulty in
keeping out this kind of weed as well as others.

In this survey of aboriginal America we have been impressed by the
contrast between two diverse aspects of the control of human activities
by physical environment. We saw, in the first place, that in our own
day the distribution of culture in America is more closely related to
climatic energy than to any other factor, because man is now so advanced
in the arts and crafts that agricultural difficulties do not impede him,
except in the far north and in tropical forests. Secondly, we have found
that, although all the geographical factors acted upon the Indian as
they do today, the absence of metals and beasts of burden compelled man
to be nomadic, and hence to remain in a low stage of civilization in
many places where he now can thrive. In the days long before Columbus
the distribution of civilization in the Red Man's Continent offered
still a third aspect, strikingly different both from that of today and
from that of the age of discovery. In that earlier period the great
centers of civilization were south of their present situation. In
the southern part of North America from Arizona to Florida there are
abundant evidences that the Indians whom the white man found were less
advanced than their predecessors. The abundant ruins of Arizona and New
Mexico, their widespread distribution, and the highly a