But the most interesting specimen was found in an old pit near the Minnesota Mine. In removing the accumulated leaves and vegetable mould, the workmen, at the depth of eighteen feet, discovered a mass of copper ten feet long, three feet wide, and more than a foot thick, weighing six tons. On removing the earth around the mass, it was found to rest upon skids, or timbers, piled up to the height of about five feet. These timbers, having been constantly covered with water, were in a good state of preservation, and at the ends showed plainly the marks of the tool used in cutting them. It was thought by those who saw the billets when they were plump, that they were a species of oak; but the few remaining pieces which I have seen were so cracked and shrivelled that I have been unable to form an opinion as to the kind of wood. This mass of copper, like all others found in those ancient pits, was divested of all its ragged points, and hammered perfectly smooth. There was nothing in its appearance to show that it had ever been cut from another mass; but upon clearing out the rubbish from the bottom of the mine, which was about twenty-six feet below the surface, a vein of pure metal was found from which this had evidently been taken. A few unfinished jobs have been found in these ancient pits, which throw some light upon the manner in which the work was carried on. In two instances there were projecting masses somewhat resembling urns, or inverted short-necked bottles, and completely smoothed by hammering, especially at the thinner portion or neck. It appears that the ancient miners first removed the rock from around the veins of copper. This was done by building fires upon or about it, and, when heated, crumbling it by throwing on water. By means of stone mauls the fragments were broken up and removed. When the vein was sufficiently exposed on all sides, a point was selected where the copper was thinner or narrower than the average of the vein. Here they commenced cutting off a mass, and by patient and long-continued hammering severed the two portions of the vein. In all the ancient mines which I have visited there is abundant evidence that fire was extensively used in the removal of rock; for not only do the rocks give proof of having been heated, but charcoal and ashes are invariably found at the bottom of all the rock excavations. In general, the mining was done by surface openings along the line of the outcrop of the vein; but occasionally adits are driven into the rock, similar to the one first discovered at the Minnesota Mine before alluded to.