habitants of some parts of the Western prairies dwelt in
tents. These were next exchanged for the "dugout," and this for a rude
hut. Subsequently the rude hut was made into a barn or pig-pen, and a
respectable farmhouse was built; and finally this, too, has been
replaced by a house of modern style and conveniences. If we could
consider this change to have extended over thousands of years, from the
first shelter of man to the finished modern building, it would be a
picture of the progress of man in the art of building. In this slow
process man struggled without means and with crude notions of life in
every form. The aim, first, was for protection, then comfort and
durability, and finally for beauty. The artistic in building has kept
pace with other forms of civilization evinced in other ways.

One of the most interesting exhibits of house-building for protection
is found in the cliff dwellings, whose ruins are to be seen in Arizona
and New Mexico. Tradition and other evidences point to the conclusion
that certain tribes had developed a state of civilization as high as a
middle period of barbarism, on the plains, where they had made a
beginning of systematic agriculture, and that they were afterward
driven out by wilder tribes and withdrew, seeking the cliffs for
protection. There they built under the projecting cliffs the large
communal houses, where they dwelt for a long period of time.
Subsequently their descendants went into the valleys and developed the
Pueblo villages, with their large communal houses of _adobe_.

_Discovery and Use of Metals_.--It is not known just when the human
race first discovered and used any one of the metals {101} now known to
commerce and industry, but it can be assumed that their discovery
occurred at a very early period and their use followed quickly.
Reasoning back from the nature and condition of the wild tribes of
to-day, who are curiously attracted by bright colors, whether in metals
or beads or clothing, and realizing how universally they used the
minerals and plants for coloring, it would be safe to assume that the
satisfaction of the curiosity of primitive man led to the discovery of
bright metals at a very early time. Pieces of copper, gold, and iron
would easily have been found in a free state in metal-bearing soil, and
treasured as articles of value. Copper undoubtedly was used by the
American Indians, and probably by the inhabitants of Europe during the
Neolithic Age