One remarkable mining excavation of the Mound-Builders was found near the Waterbury mine. Here, in the face of a vertical bluff, was discovered “an ancient, artificial, cavern-like recess, twenty-five feet in horizontal length, fifteen feet high, and twelve feet deep. In front of it is a pile of excavated rock on which are standing, in full size, the forest trees common to this region.” Some of the blocks of stone removed from this recess would weigh two or three tons, and must have required levers to get them out. Beneath the surface rubbish were the remains of a gutter or trough made of cedar, placed there to carry off water from the mine. At the bottom of the excavation a piece of white cedar timber was found on which were the marks of an axe. Cedar shovels, mauls, copper gads or wedges, charcoal, and ashes were discovered, over which “primeval” forest trees had grown to full size. Modern mining on Lake Superior began effectively in 1845. The whole copper region has not been fully explored. Works of the ancient miners are found at all the mines of any importance; and they show remarkable skill in discovering and tracing actual veins of the metal. Colonel Charles Whittlesey, one of the best authorities on this point, believes the Mound-Builders worked the copper-beds of that region during “a great length of time,” and more of their works will undoubtedly be explored when the forests shall be cleared away from those portions of the copper region not yet worked by modern miners. So far as they have been traced, they every where show the same methods, the same implements, and the same peculiarities of both knowledge and lack of knowledge in the old miners. II. ANTIQUITY OF THE MOUND-BUILDERS. That the Mound-Builders and their works belong to a distant period in the past is evident; but, of course, we have no means of determining their antiquity with any approach to accuracy, no scheme of chronology by which their distance from us in time can be measured. Nevertheless, some things observed in their remains make it certain that the works are very ancient.