602 



THE POPULAR SCIENCE MONTHLY, 



copper to a tliin 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 sum- 

 mer 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 ]Dounds, the latter being about nine feet 

 long. The largest mass yet found at that place was taken out the pre- 

 vious 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 de- 

 tached from the inclosing rock, though it was wholly uncovered and 

 undermined. A restoration of its appearance, as represented by Cap- 

 tain William Jacka, is seen in Fig.. 1. 



3 Natural Surface 3 







- : 



Fig. 1. a, mass of copper ; b, the inclosinj? rock ; c, layer of drift excavated, twelve feet thick ; 

 (1 d, line showing surface of the ancient pit before reexcavation. 



Various articles have been found in these old pits or in their neigh- 

 borhood. 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 



