Mr Hugh Miller on River- Terracing. 



287 



divert large bodies, or even the whole, of the main stream. 

 Shifting curves may tlien play for a time along the edge of 

 the future terrace with much of tlie force exerted by more 

 persistent ones, cutting their way laterally in the oblique plane 



Fig 12. 



"GLacis Terraces" (Wliickhope Burn, North Tyne). 



Scale — both horizontal and vertical — 1 inch = 60 yards. 



which planation accompanied by deepening must necessarily 

 follow. When left thus, glacis-terraces result. The angle of 

 the glacis slopes shown in the transverse section (Fig. 12) 

 does not exceed IJ degree; it sometimes attains at least as 

 much as 5. 



Lateral Terraces: 2. Junction Terraces. 



At the junction of streams there is a manifest tendency in 



both currents to keep clear of what lies in the angle between 



them. A spit of gravel is apt to accumulate (by accretion of 



materials stranded on their way down-stream) at the point, 



Fig. 13. 



Terraces preserved at a junction of streams (Chirdon Burn, North Tyne), 



Scale — 3 inches = 1 mile. 



and by continual growth may in time form a triangular flat. 

 Thus are constructed planes, which periodical destruction at 

 successive levels may convert into terraces ; and the means 

 of periodical destruction are close enough at hand. The 



