AND OTHER WATER WAVES 311 



transmission of a wave with an amplitude from 

 trough to crest of 6.5 inches. I think the dis- 

 crepancy, however, is to be explained not so much 

 by this circumstance as by an error introduced by 

 the determination of the velocity of the current. 

 I made a note at the time that the floating objects 

 which I was observing were several times caught 

 and pushed along by the foaming front of the 

 waves . Thus their speed was probably greater than 

 the average velocity of the current, making the 

 wave -velocity come out too low. 



On some occasions the failure of the stream 

 just before the arrival of the crest was distinctly 



noticeable a fact in itself, and apart from the 

 i 



measurements, indicating that the waves differ more 

 in appearance than in essence from ordinary waves . 

 The waves had not completed their growth when 

 they reached the outflow ; but if the length of 

 the conduit could be much increased, we should 

 doubtless see the last part of the course traversed 

 by a series of waves of uniform height, length, and 

 speed, as occurred after a short run in the 

 shallower, but smoother, conduit of the Territet- 

 Glion Funicular Railway. 



The following table shows the number of wave- 

 crests passing per minute at different distances from 

 the entrance of the channel, taken on several days, 



16 



