66 THE OCEAN 



feet In situations such as these the bottom 

 of the incoming tide "drags" and the tide, in- 

 stead of rising gradually as on most coasts, 

 approaches in the form of an immense wave 

 and often travels with great speed, its crest 

 curling and foam-capped like a huge roller 

 breaking on a beach. 



These great "tidal waves" are called "bores" 

 and frequently boats are destroyed and lives 

 lost by being caught in the irresistible, oncom- 

 ing tidal "bore." 



We speak of the mass of water, supposedly 

 attracted by the moon and which produces 

 our tides, as a "tidal wave," but in reality 

 this is not a true wave at all and is very dif- 

 ferent indeed from another kind of "tidal 

 wave." 



While the so-called tidal wave is a mass of 

 water which actually moves along, the water 

 in true waves does not move forward but 

 merely up and down, although the waves 

 themselves move forward. The fact that the 

 water of waves moves only up and down is 

 easily proved by tossing a bit of wood upon the 

 water and, if no tide is flowing and no wind 



