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Page:Popular Science Monthly Volume 19.djvu/620

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copper to a thin layer by pounding it continuously on the same side. The finding of these thin chips of copper is the first indication to the present miners of the proximity of a large mass. In the summer of 1874 the first of these large masses was discovered. It was sixteen and one half feet below the surface, and under it were poles, as if it had been entirely detached, but it had not been much displaced. This mass was exhibited publicly in the yard of the court-house at Detroit, and was also on exhibition at the Centennial Exposition in 1876. It was subsequently fused and sold as commercial copper. It weighed 5,720 pounds, and has been described by Mr. Henry Gillman, in the annual volume of the American Association for the Advancement of Science for 1875. In the summer of 1879 two other large masses that had been wrought by the ancients were found at the Minong Mine, which is at the head of McCargoe's Cove. One had a weight of 3,317 pounds, and the other 4,175 pounds, the latter being about nine feet long. The largest mass yet found at that place was taken out the previous summer, weighing six tons, but the ancients had not discovered it, though one of their drifts ran within two feet of it. The large masses discovered by the ancients show the labor that has been spent on them in their hammer-marked and pitted surfaces. They seem to have been beaten up into ridges and points, by hammering alone, for the easier removal of parts. One of those found in 1879 was not detached from the inclosing rock, though it was wholly uncovered and undermined. A restoration of its appearance, as represented by Captain William Jacka, is seen in Fig.. 1.

PSM V19 D620 Lines of excavation in isle royale copper mine.jpg

Fig. 1.a, mass of copper; b, the inclosing rock; c, layer of drift excavated, twelve feet thick; d d, line showing surface of the ancient pit before reëxcavation.

Various articles have been found in these old pits or in their neighborhood. Several copper implements, such as a gad, a chisel, knives, and arrow-heads, have been discovered, both on Isle Royale and in the vicinity of similar old mines on the south shore of Lake Superior. Mr. Gillman reports that a large part of a "wooden bowl," originally about three feet in diameter, which had probably been used for boiling water, was taken from one of these pits. The timber found in some