afterwards, arable areas were limited, hence they were compelled to
divide into families or small clans, each occupying a single house.
The traces of these solitary farm-houses show that they were at first
single-storied. The name of an upper room indicates how the idea of
the second or third story was developed, as it is _ósh ten u thlan_,
from _ósh ten_, a shallow cave, or rock-shelter, and _ú thla nai e_,
placed around, embracing, inclusive of. This goes to show that it was
not until after the building of the first small farm-houses (which
gave the name to houses) that the caves or rock-shelters of the
cliffs were occupied. If predatory border-tribes, tempted by the
food-stores of the horticultural farm-house builders, made incursions
on the latter, they would find them, scattered as they were, an easy
prey.


ADDED STORIES FOR CLIFF DWELLINGS DEVELOPED FROM LIMITATIONS OF
CLIFF-HOUSE SITES.

[Illustration: FIG. 498.--A typical cliff-dwelling.]

This condition of things would drive the people to seek security in
the neighboring cliffs of fertile canons, where not only might they
build their dwelling places in the numerous rock-shelters, but they
could also cultivate their crops in comparative safety along the
limited tracts which these eyries overlooked. The narrow foothold
afforded by many of these elevated cliff-shelves or shelters would
force the fugitives to construct house over house; that is, build a
second or upper story around the roof of the cavern. What more
natural than that this upper room should take a name most descriptive
of its situation--as that portion built around the cavern-shelter or