Remains of their mining works were first discovered in 1848 by Mr. S. O.
Knapp, agent of the Minnesota Mining Company, and in 1849 they were
described by Dr. Charles T. Jackson, in his geological report to the
national government. Those described were found at the Minnesota mine,
in upper Michigan, near Lake Superior. Their mining was chiefly surface
work; that is to say, they worked the surface of the veins in open pits
and trenches. At the Minnesota mine, the greatest depth of their
excavations was thirty feet; and here, "not far below the bottom of a
trough-like cavity, among a mass of leaves, sticks, and water, Mr. Knapp
discovered a detached mass of copper weighing nearly six tons. It lay
upon a cob-work of round logs or skids six or eight inches in diameter,
the ends of which showed plainly the marks of a small axe or cutting
tool about two and a half inches wide. They soon shriveled and decayed
when exposed to the air. The mass of copper had been raised several
feet, along the foot of the lode, on timbers, by means of wedges." At
this place was found a stone maul weighing thirty-six pounds, and also a
copper maul or sledge weighing twenty-five pounds. Old trees showing 395
rings of annual growth stood in the debris, and "the fallen and decayed
trunks of trees of a former generation were seen lying across the pits."
Figure 19 (opposite) presents a section of this mining shaft of the
Mound-Builders: _a_ shows the mass of copper; _b_ the bottom of the
shaft; _c_ the earth and debris which had been thrown out. The dark
spots are masses of copper.
The modern mining works are mostly confined to that part of the copper
region known as Keweenaw Point. This is a projection of land extending
into Lake Superior, and described as having the shape of an immense
horn. It is about eighty miles in length, and, at the place where it
joins the main land, about forty-five miles in width. All through this
district, wherever modern miners have worked, remains of ancient mining
works are abundant; and they are extensive on the adjacent island, known
as Isle Royale. The area covered by the ancient works is larger than
that which includes the modern mines, for they are known to exist in the
dense forests of other districts, to which the modern mining has not
yet been extended.
[Illustration: Fig. 19.--Ancient Mining Shaft.]
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.