After they discovered the mines and began to work them, their progress could not have been rapid. As their open trenches and pits could be worked only in the summers, and by methods that made their operations much slower than those of modern miners, no great advance of their work was possible during the working time of each season; and yet remains of their mining works have been discovered wherever mines have been opened in our day; and, as previously stated, they are known to exist in heavy forests, where the modern mining works have not yet been established. There is nothing to indicate that they had settlements any where in the mining region. Colonel Whittlesey, and others whose study of the subject gives their opinion much weight, believe the Mound-Builders went up from the settlements farther south in the summers, remained in the copper region through the season, and worked the mines in organized companies until the advance of winter terminated their operations. Colonel Whittlesey says: “As yet, no remains of cities, graves, domiciles, or highways have been found in the copper region;” and adds, “as the race appears to have been farther advanced in civilization than their successors, whom we call aborigines, they probably had better means of transportation than bark canoes.” It may be said, also, that the accumulations called wealth were necessary to make this regular and systematic mining possible. Without these they could not have provided the supplies of every kind required to sustain organized companies of miners through a single season. A great many summers must have passed away before such companies of miners, with all needed tools and supplies, could have made their works so extensive by means of such methods as they were able to use. They probably occupied the country on the Gulf and Lower Mississippi much longer than any other portion of the great valley. Their oldest and latest abandoned settlements appear to have been in this region, where, we may reasonably suppose, they continued to dwell long after they were driven from the Ohio Valley and other places at the north.