30 THE CRYSTAL FALLS IRON-BEARING DISTRICT. 



scoring of the rocks and the character of the drift material, a good jDortion 

 of which can be readily seen to have been brought from some other region, 

 no such rocks as those forming it existing where the bowlders now lie. The 

 ice-sheet left a deposit of drift, and we find the pre-Glacial topography essen- 

 tially modified by it. As a result of this, the prevailing and most noticea- 

 ble topography of the western half of the Crystal Falls district is that of the 

 drift, and is characterized by short ridges and broken chains of hills, usually 

 oval, though at times of very irregular outline, between which are lakes 

 and swamps. The swamps are even occasionally found on rather steep 

 slopes, where a thick spongy' carpet of moss (sphagnum) retains sufficient 

 moisture for cedars and other trees and shrubs characteristic of the Michigan 

 swamps to grow. The swamps follow the carpet of moss up the hills to the 

 spring line. 



The Glacial drift topography is especially marked where the drift was 

 of considerable depth. These conditions are well exhibited in parts of 

 T. 45 N., Rs. 31, 32 "W., shown on the large-scale map, PL VIII. Here, 

 even though the ground is very heavily timbered, one may easily trace out 

 the sinuous course of the eskers. When traversing the country, one is 

 constantly descending into pot-holes or is climbing ridges, some of them 

 75 to 100 feet high, often with a crest only a few feet, in some places not 

 more than 4 feet, wide. 



"Where the drift mantle has been removed, the rovmded character of 

 the rock exposures is usually shown. This holds good especially for the 

 more resistant rocks, such as the granites and massive greenstones. Slates 

 and tuffs, weathering more readily, have in numerous cases had time since 

 the ice retreated to be weathered into rough broken ledges, some of which 

 show perpendicular cliff's. 



The elevations range usually from 1,400 to 1,600 feet above sea-level. 

 The hills rarely rise more than 200 feet above the low ground at their bases. 

 The extremes of height noted in the district are from 1,250 to 1,900 feet 

 above sea-level, corresponding, respectively, to the valley of the Michigamme 

 on the south and the watershed between Lake Superior and Lake Michigan 

 on the north. Between these two extremes there is a strip of territory, 25 

 miles across from north to south, in which the variations in height are 

 within the limits of 200 feet. 



A consideration of the slight difference of level whicli prevails over 



