292 WAVES OF THE SEA 



waves in rivers, and I was on the look-out more 

 particularly for waves facing down -stream and pro- 

 gressing through the water in a down -stream direc- 

 tion. Such waves would, of course, pass the bank 

 more rapidly than the water itself, for their apparent 

 velocity would be that of the current plus the 

 proper motion of the wave. 



Near Devil's Hole Station, opposite to Foster's 

 Elats, on the rapids below the Whirlpool, I observed 

 that from time to time freshets came down the 

 river, raising the level of the water on the bank for 

 as much as 90 seconds. Thus at 1 1 hours 

 26 minutes 5 seconds a large freshet arrived, rais- 

 ing the general level of the water about 12 inches. 

 Duration of high water, ij minutes. 



1 1 hours 32 minutes 5 seconds, another freshet ; 

 high water, i minutes. 



1 1 hours 37 minutes 5 seconds, a small freshet. 



1 1 hours 42 minutes 5 seconds, a small freshet. 



I could not, however, perceive any visible travel- 

 ling wave, nor was there anything to indicate that 

 these freshets travelled faster than the current. If 

 they had been due to " long waves " progressing 

 in the direction of the stream, they would have been 

 travelling at some much greater velocity, perhaps 

 twice as fast, for the depth here is very consider- 

 able. I am inclined to think, therefore, that this 



