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 12 ABORIGINAL MONUMENTS

broad and deep, and occasionally quite symmetrical in shape. In the vicinity of large mounds, such excavations are also common.*

A large, perhaps the larger, portion of these works are regular in outline, the square and the circle predominating, Some are parallelograms, some ellipses, others polygons, regular and irregular. The regular works-are almost inva- riably erected on level river-terraces, great care having evidently been taken to select those least broken. The irregular works are those which partake most of the character of defences, and are usually made to conform to the nature of the ground upon which they are situated— running along the brows of hills, or cutting off the ap- proaches to strong natural positions. The square and the circle often occur in combination, frequently communicat- ing with each other or with irregular works, directly or by avenues consisting of parallel lines of embankment. Detach- ed parallels are frequent. The mounds are usually simple cones in form, but they are sometimes truncated, and occa- sionally terraced, with graded or winding ascents to their summits. Some are elliptical, others peariform, and others squares or parallelograms, with flanking terraces. Besides these there are others, most common in the extreme north- west, which assume the forms of animals and reptiles. Another variety of remains are the causeways or “roads,” and the graded descents to rivers and streams, or from one terrace to another.

As already remarked, these remains occur mainly in the valleys of the Western rivers and streams. The allu- vial terraces, or “river bottoms,” as they are popularly termed, were the favorite sites of the builders. The prin- cipal monuments are found where these “bottoms” are most extended, and where the soil is most fertile and easy

Antiquities. It is barely possible that a few were really wells, or secondarily designed for reservoirs.
 * These are the “ wells” of Mr. Atwater and other writers on American