These mounds are divided into three classes, according to their use. The most northern remains of the Mound-builders yet discovered are on the southern shore of Lake Superior, and in the valley of the Wisconsin River. All of these mounds are representations of animals on a gigantic scale—hence we will call them _effigy_ mounds—and seem to represent their religious rites. No other mounds are found here, which was not a place of residence, and this character of mound is not found elsewhere except the great Serpent Mound in Adams County, Ohio. Around Chicago the mounds are not more than twelve feet high, but in Iowa they were so plentiful that the French named the river in that State “Des Moines,” which means “the mounds.” Where St. Louis stands was once so thickly studded with mounds, that the city has been called “The Mound City.” In the State of Mississippi the largest river was so thickly strewn with these prehistoric ruins that the Choctaws called it “_Yazoo-okhinnah_”—“The River of Ancient Ruins.” In Illinois the mounds are oblong, square, ellipsoidal and conical. Cahokia, the largest mound in the United States, stood here. It formed a parallelogram with sides respectively seven hundred and five hundred feet long and ninety feet high, and covered fifteen acres—larger than the largest pyramid in Egypt. On the top of this mound was probably a temple, for many bones and funeral vases were taken from the interior; so we call this a _temple_ mound. The banks of the Ohio, Scioto, Wabash and Muskingum are so thickly covered with mounds and tumuli, that Squier and Davis estimate that Ohio alone contains ten thousand, and plainly indicate that this was the capital of the Mound-builders’ empire. A number of these are conical mounds, and the bones and charcoal indicate that they were _sacrificial_ mounds. Near Newark, Ohio, occur the most stupendous of the Mound-builders’ works, covering two square miles, and containing walls, pyramids, circles and turrets, which in our day, with machinery and horse-power, would require many thousand men many months to perform. One of the wonders of the world is the great Serpent Mound in Adams County, Ohio, which stamps the religious character of the vanished race. The total length of the serpent is fourteen hundred and fifteen feet, and the distance between the jaws one hundred feet. It lies on the crest of a hill, and its folds correspond with the windings of the hill. Is this serpent an emblem of the one that plays such a part in the mythology of the old world? “This symbol prevails in Egypt, Greece, Assyria, and among the superstitions of the Celts, Hindoos and Chinese. Wherever native religions have had their scope, this symbol is sure to appear.”