Chapter IV 



TIDES AND WAVES 



Some of the greatest mysteries of the sea are 

 of such everyday occurrence and so familiar 

 to us that we seldom give them more than 

 passing thought or stop to realise how really 

 remarkable they are. Among them are the 

 tides, and while we all know that tides occur 

 and we look upon them as a matter of course, 

 yet they are really very strange and myste- 

 rious things and are difficult to explain satis- 

 factorily. We attribute the rise and fall of 

 the tides to the moon, but after all we really 

 have no proof that the moon causes them, 

 and our reason for believing that they are 

 produced by that planet's influence is mainly 

 due to theory and our knowledge of certain 

 natural laws. 



For a very long time man has noticed that 

 the intervals of the tides correspond with the 



time of the moon's passage, and as we know 



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