BY E. C. ANDREWS. 807 



action oT floods along disused wagon tracks, or " tailraces"* used 

 in alluvial mining. The largest examples known to the writer 

 in New England are 50 feet deep, and the greatest age known is 

 50 years. But, whereas the ordinary road-gutter is wholly 

 occupied by storm-waters, the bases only of the young canons 

 under consideration are so occupied. If attention be confined to 

 the lowest portions only of these gulches there will be found 

 basins, U-shaped sections, and stretches of channel-base recti- 

 linearly disposed, all similar to those found along the gutters. 

 This lower portion is that which is occupied by the heaviest 

 storm-waters. Above these flood-channels one finds V-shaped 

 valley-sections and the other characteristics of valley-slopes 

 which have been determined mainly by weathering and stream 

 trickles. It will be found also that hanging valleys occur along 

 these lower portions in positions similarly situated to those along 

 ordinary road-gutters. 



The accompanying sketch illustrates contours of a tiny cafion 

 at Uralla, New England. The observations here recorded deserve 

 careful consideration, inasmuch as they throw considerable light 

 on the characteristic contours of fiords and Alpine lake-regions. 



3. Brook and river-channel coyitours. — These will be found to 

 represent features very similar to those of incipient canons. 

 One or two distinctions may be drawn, however, between the 

 types, whereas the flood-channel of the incipient canon occupies 

 a considerable fraction of the whole valley, the flood-channels of 

 ordinary brooks and rivers generally occupy but an insignificant 

 portion of their containing valleys. Again, the incipient cafion 

 is but the product of a few years' stream-corrasion, and as such 

 its features stand out plainly; whereas the ordinary stream- 

 developed valley, representing, possibly, the action of streams 

 during millions of years, has its contours softened and partially 

 concealed beneath rock-waste and vegetation. Yet the frequent 



* A "tailrace," in Australian alluvial mining, aignifies a small channel 

 situated below ground-sluicing operations, and employed as a " getaway " 

 for the earthy material associated with the valuable minerals. 

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