48 Wisconsin Acadenuj of Sciences^ Arts and Letters. 



been determined in each case, the size, shape and condition 

 of the specimens, and their frequency in any locality, this 

 might give us the data required for explaining the dispersion. 

 There appear to be localities where the copper is more abund- 

 ant than at others, as at Grand Traverse Bay, at the mouth 

 of the Illinois river^ and along the lower course of the Wa- 

 bash. The seemingly greater abundance at these points, 

 however, may only be due to fuller observation or record 

 of the metal found at these points, and not to its really 

 greater prevalence. 



It may not be out of place to call attention to the probable 

 fact that the Illinois river, about whose mouth many speci- 

 mens have been found, was once the outlet of Lake Michi- 

 gan, and that the Wabash, about whose lower course much 

 copper has also been found, was the channel for discharge, 

 in post-glacial times, of Lake Erie. It is evident that if the 

 copper were all transported from Lake Superior by glaciers, 

 they must have had, at different periods, very divergent 

 courses to account for the east-west dispersion. The fact that 

 copper has been found in the red clay both of Lake Superior 

 and Lake Michigan, suggests that along the lake borders, 

 pieces of copper may have been dropped by floating ice, and 

 the roughness of at least a portion of the specimens here 

 found, is in harmony with such a view. 



There is of course a possibility in all cases, and this possi- 

 bility may at times amount to probability, that the disper- 

 sion of copper has been by human agencies. A single loose 

 specimen, for instance, has been found in the " driftless 

 area " in Jo Daviess county, Illinois, in a rock crevice. But 

 in regions where frequent specimens are found scattered 

 through the drift, there is little probability that their occur- 

 rence can be explained by human transportation. 



Dr. Bell, of the Canada Survey,' has described a formation 

 on Hudson's Bay, which has a strong resemblance to our 

 Keweenawan system. He has indicated his belief that the for- 

 mation is the equivalent of the Nipigon group, which is sup- 

 posed to be continuous with the Keweenawan, and, therefore, 

 its equivalent. Dr. Bell describes copper sulphide in the as- 



1 Geological Report, 1878. 



