THE GLACIAL DRIFT. q-^q 



red matrix itself develops large crystalline faces; and still others in 

 which the aphanitic matrix constitutes the whole rock. 



Quartzite bowlders are not at all common except in one or two lim- 

 ited districts. One of these is in eastern Dane county, in the towns 

 of Medina and Deerfield, where they are abundant, and associated 

 with bowlders of conglomerate, both having beyond doubt come from 

 a mound of quartzite a few miles northeast in Dodge county. It 

 might be expected that the Baraboo quartzite ranges would have had 

 their rock scattered very widely in the country to the southward, but 

 this is not the case. In the Baraboo valley, and still more in the 

 country immediately south of the ranges, quartzite bowlders of large 

 size are very abundant. Further south they occur sparingly as far 

 as the region about Lodi, including talcose quartz-slate, also undoubt- 

 edly from the Baraboo ranges. Still further south they are more no- 

 ticeable for their absence than their presence. It will be seen that 

 this rather unexpected fact admits of a very satisfactory explanation. 

 Sandstone bowlders are rare, not because sandstone is not abundant 

 in the regions over, which the drift movement took place, but because of 

 the very friable nature of the rock. Those sandstone bowlders that are 

 found are always either somewhat quartzitic, or, as is more frequent- 

 ly the case, are rendered hard by a large amount of cementing brown 

 iron oxide. Amongst the smaller materials of the drift are sometimes 

 found hard ferruginous concretions which are recognized as coming 

 *from the great sandstone region of the heart of the state. That large 

 limestone bowlders should be so very rare appears to be due to the 

 ease with which that rock is worn into smaller sizes. 



One of the most interesting substances found in the drift, though 

 hardly attaining the size of a bowlder, is the native copper, which is 

 found in fragments widely scattered over the northwest, from Ohio to 

 Minnesota. These native copper fragments are far more abundant 

 in Wisconsin than elsewhere, and far more abundant there than is 

 commonly supposed. Specimens weighing from a few ounces up to 

 30, 40, and even 50 pounds, are constantly found in digging. The 

 late Dr. Lapham informed me that the coppersmiths in Milwaukee 

 purchased from finders yearly several hundred pounds of this copper. 

 Ancient implements of copper have been found very abundantly in 

 Wisconsin, the largest collection of such relics in the world now being 

 in possession of the State Historical Society at Madison. It has been 

 argued that these implements prove a high degree of civilization for 

 the races that occupied the northern United States in remote times, 

 since copper smelting is an art unknown to the more barbarous peo- 

 ples. It is evident enough, however, that there is a direct connection 



