306 WAVES OF THE SEA 



ling another 554 feet (or 1,121 feet in all), there 

 were 20 waves passing every second ; the height 

 and length of the waves having increased propor- 

 tionately, and the depths at the troughs being 

 correspondingly diminished. The current is much 

 accelerated at and near the crests, and considerably 

 diminished in speed at the troughs, as is readily 

 seen by watching the progress of small floating 

 bodies. 



At the outfall into the lake, a further dis- 

 tance of 240 feet, or 1,361 feet in all, the waves 

 were 1 7 per minute . The outfall of water is often 

 twice or three times as great when a roll -wave crest 

 arrives as at other times. The fall of the roll-wave 

 is accompanied by a booming noise, and the flash 

 of the outflowing water is sometimes visible at a 

 distance of 2 miles. 



On September 16, 1904, with a uniform depth 

 in the upper part of the channel of 3 inches to 

 3^ inches, as nearly as could be determined, the 

 water at the outflow had a depth of 8 inches at 

 the crests and i J inches at the troughs of the waves . 

 The time of flow of the water from entrance to exit 

 of the paved channel was 90.2 seconds a short 

 time indeed for the evolution of such a cadence 

 from a mere flicker, and for the development of a 

 wave amplitude from, say, ^o inch to at least 6 



