AND OTHER WATER WAVES 101 



The diagrams, which I published in Knowledge 

 in 1 90 1, and afterwards in the Geographical Journal, 

 May, 1904, show what is geometrically and 

 numerically possible in the way of such obscuration. 

 The observations made on the north coast of 

 Ireland by Sir G. G. Stokes (as well as my own 

 observations) show how necessary it is to allow 

 for the presence with the storm -waves of longer 

 waves of considerable amplitude. Abercromby's 

 single observation supplies a confirmation of the 

 apparently somewhat extreme case shown in the 

 figure given on p. 98. It is, however, much 

 to be desired that further observations similar to 

 those of Abercromby should be obtained, for it 

 must be confessed that it is a narrow foundation 

 upon which to build. 



On the Co-existence of Waves of Different Lengths 



In studying deep-sea waves one is often called 

 upon to decide whether to fix the attention upon 

 the actual surface of irregular or complex form 

 and deal with it as the concrete wave, or to think 

 of this irregular wave as composed of, or resolved 

 into, a number of simple harmonic waves each of 

 regular form and of a different speed. As a matter 

 of mathematics all irregular waves can be so re- 



