Mr TIiujli Miller on Riccr-Tcrracinfj. 275 



ways, eating out a curve. The sliape of tlie bottom changes. 

 The apex of the V or U, which its cross-section may have 

 originally resembled, is forced to one side. The water, heaped 

 up and recoiling, bears against the obstructing bank and 

 bottom; the one is scarped into a cliff, and the other is 

 scooped into a pool. After having rounded the curve thus 

 made, the stream shallows and passes on. One curve, how- 

 ever, propagates another. After being deflected from one bank 

 the stream is projected against the other ; and thus results 

 that succession of curves and pools with which every one 

 who has had to do with rivers, whether as fisherman, or 

 bargeman, or engineer, is so familiar. The pools so formed 

 may be termed cUfledion-iwoh!^ 



Travelling of llivev -Curves and Deflection- Pools. 



The bends in a stream acting as partial dams in its course,i" 

 and the water in beino- thrust back and turned aside, gnaw- 

 ing ceaselessly at the bank which deflects it, deflection-pools 

 and the scars or cliffs that border them, are never perfectly 

 stationary. They are all being worked more or less in the 

 direction of stream- flow ; many of them tend, upon the whole, 

 to travel down the valley. When the stream works among 

 soft materials these movements can be measured ; in floods 

 they may render themselves alarmingly self- evident. Tylor 

 cites a case in which a deflecting bank of the Ganges travelled 

 150 feet laterally in one flood. During the famous Moray- 

 shire floods of 1829 this figure must have been frequently 

 approached. There is an interesting paper in the Proceedings 

 of this Society showing, by a chart, the effects of a violent 



* Dr James Geikie has applied the term deflection-Jasiji to certain lakes, — 

 on Ramsay's theory, glacier-scooped, — lying adjacent to high grounds against 

 which the ice-streams of the Glacial Period abutted. It is well that pheno- 

 mena so analogous should have analogous names. In British rivers deflection- 

 pools are pools only. In such gigantic rivers as the Amazon and Mississippi 

 they are lake-like ; and when isolated by those shifts of channel known as 

 " cut-offs " form lakes often 10 br 12 miles in length. The ^v^ite^ has else- 

 where had occasion to point out the importance of deflection-pools, as carrying 

 out the analogy between rivers and glaciers in view of the supposed lake-form- 

 ing power of the latter (Geol. Mag., 1877). 



t Humphreys and Abbot, Physics and Hydraulics of the Mississippi, 1S76, 

 p. 333. 



