It is a fact but recently made known, that there are an abundance of small mounds, or tumuli, in the territory of Oregon. We are not informed, however, whether there are any enclosures, or other works of like character with those usually accompanying the mounds of the Mississippi valley, nor whether the mounds of Oregon are generally disseminated over that territory.[2] That they are of frequent occurrence upon the river Gila, in California, and also upon the tributaries of the Colorado of the West, is also a fact but recently ascertained. Whether these mounds possess features identifying them with those of the Mississippi valley, or indicating a common origin, remains to be decided.
It is not to be understood that these works are dispersed equally over the area above indicated. They are mainly confined to the valleys of the rivers and large streams, and seldom occur very far back from them. Occasional works are found in the hill or broken country; but they are not frequent, and are always of small size.
Although possessing throughout certain general points of resemblance, going to establish a kindred origin, these works, nevertheless, resolve themselves into three grand geographical divisions, which present, in many respects, striking contrasts, yet so gradually merge into each other, that it is impossible to determine where one series terminates and the other begins. In the region bordering the upper lakes, to a certain extent in Michigan, Iowa, and Missouri, but particularly in Wisconsin, we find a succession of remains, entirely singular in their form, and presenting but slight analogy to any others of which we have an account, in any portion of the globe. The larger proportion of these are structures of earth, bearing the forms of beasts, birds, reptiles, and even of men; they are frequently of gigantic dimensions, constituting huge «basso-relievos» upon the face of the country. They are very numerous, and in most cases occur in long and apparently dependent ranges. In connection with them, are found many conical mounds and occasional short lines of embankment, in rare instances forming enclosures. These animal effigies are mainly confined to Wisconsin, and extend across that territory from Fond du Lac, in a south-western direction, ascending the Fox river, and following the general course of Rock and Wisconsin rivers to the Mississippi. They may be much more extensively disseminated; but it is here only that they have been observed in considerable numbers. In Michigan, as also in Iowa and Missouri, similar elevations, of more or less regular outline, are said to occur. They are represented as [p003] dispersed in ranges, like the buildings of a modern city, and covering sometimes an area of many acres.