CHAPTER X 



Stationary or standing waves Cross-stream progressive 

 waves : observations in Niagara River. 



Stationary or Standing Waves 



ONE who observes the well-known waves of rapid, 

 or rock -encumbered, rivers from the bank cannot 

 fail to notice that whereas the shape of the corru- 

 gated surface is not very different from that of an 

 agitated sea, yet there is this great difference, viz., 

 that the river -waves maintain their position un- 

 changed ; and, partly for this reason, they are 

 called stationary or standing waves. If a piece 

 of stick be tossed* upon the stream, its down- 

 stream motion over the corrugated surface will be 

 seen to be alternately checked and accelerated as 

 it reaches the crests and troughs respectively. 

 Mathematically, this undulated river is regarded 

 as a steady stream, flowing, say, to the right, with 

 a train of waves travelling to the left at a speed 



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