AND OTHER WATER WAVES 



99 



be represented by replacing the theoretically 

 infinite number of wave-lengths by two, which 

 I call the storm -wave, or the dominant wave, and 

 the swell, the former 30 feet high and the latter 20. 

 The lengths arbitrarily chosen are 600 feet for 

 the former and 1,150 for the latter. It will be 

 noticed that the combined wave in the third line 

 represents fairly well the appearance of a toler- 

 ably regular sea, and it would do so still better 

 if the curves had been drawn in the form of a 

 trochoid instead of a curve of sines, which makes 

 the trough similar to the crest. 



Measuring from left to right, the vertical distance 

 from each crest to the trough next on the right is : 



22*50 feet 

 37-50 

 1875 

 40-00 



27-50 n 



Average 28-30 feet. 



The average, if carried on through the whole 

 gamut of the combined wave, would be 30 i.e., 

 the same as the height of the dominant or storm- 

 wave. Thus, in the above example we have 

 a range of observed wave -height from rather less 

 than 20 feet up to 40 feet. This result, correspond- 

 ing to the heights observed by me in the storm of 



