332 THE CRYSTAL FALLS IRON-BEARING DISTRICT. 



sections of T. 47 N., R. 31 W., the average elevation is 1,800 to 1,900 feet. 

 Since the intervening distance is somewhat more than 30 miles, the gen- 

 eral slope is therefore less than 20 feet to the mile. 



The minor topographical features based upon this plain are multitiidi- 

 nous in variety and detail, but generally quite insignificant in relief The 

 maximum difference of elevation between the top of the highest hill and 

 the bottom of the neighboring valley is less than 300 feet, and this is 

 reached in but two cases. The country possesses no commanding emi- 

 nences, and in the widest panoramas now and then obtainable from the 

 summits of glaciated knobs the background is restricted to a radius of a 

 few miles. In these the general evenness of the sky line is usually broken 

 only by the remnants of the old forest, which have not yet succumbed to 

 fire and the lumberman. 



These lesser features have been shaped mainly by the work of the conti- 

 nental ice-sheet, both through the materials which it brought in and through 

 those which it carried away. In the areas underlain by relatively massive 

 rocks, ^particularly the Archean crystallines, the surface has been left mam- 

 millated with rocky knobs, which doubtless were the unattacked cores rising 

 into the pre-Grlacial zone of disintegration. These are separated by the 

 similar inverse forms, now for the most part occupied by swamps. In the 

 Archean borders of the Felch Mountain area, where the glacial cover was 

 originally thin, the periodical fires that have followed lumbering operations 

 have burned out the organic matter from the soil and so loosened it that, 

 on the steeper slopes, it has been entirely washed away and the rock 

 surface laid bare. The hummocks and bowls are generally elongated east 

 and west, which is the direction both of the gneissic foliation and of the ice 

 movement. The elevations rise, often with steep, smooth walls, for 5, 10, 

 20, or even in some cases 60 feet, above the intervening depressions. The 

 latter hold muskeg to the rims. In the wet season they fill with water, 

 which overflows to the next bowl below, but permanent lines of minor 

 drainage, here as elsewhere in the Archean areas, are very infrequent. 



Over most of the area, however, the ice has spread a sheet of till, and has 

 here and there deposited the materials swept along in the subglacial streams 

 in characteristic complexity of form and grouping. The more prominent 

 elevations are, in fact, deposits of modified drift, although occasionally 



