SEA WATER 239 



math of a heavy storm or the herald of wind to come. 

 Waves are of great importance in helping to keep the surface 

 waters of the sea mixed, while in the tidal zone they have 

 left their mark in the many adaptations shown by littoral 

 animals for protection against the pounding surf. 



Waves are generally the result of the action of wind 

 on the sea surface, from the faintest ripple caused by the 

 light airs of summer to the tumultuous mountains of water 

 raised by the full force of a winter's gale (Plate 83). The 

 size of the wave depends upon the strength of the wind 

 and upon the distance through which the wind can act. 

 In open waters in mid-ocean, therefore, the largest waves 

 occur, because there the space is greatest ; and of ocean 

 waters those of the southern ocean have greatest expanse 

 and exposure- to gales, and it is there that the waves reach 

 their greatest height. The height of a wave is the vertical 

 distance between the summit of the crest and the deepest 

 point of the trough. The maximum height of waves 

 recorded by measurement are for the Mediterranean 

 seventeen feet, the Bay of Biscay twenty-seven feet, the 

 Atlantic Ocean forty feet, and the Pacific Ocean off the 

 Cape of Good Hope fifty to sixty feet. 



The speed at which a storm wave travels in the Atlantic 

 Ocean is about twenty-two miles an hour, while off Cape 

 Horn as much as twenty-seven miles an hour has been 

 recorded. 



The wave in the open ocean is of the type known as an 

 oscillatory wave. That is, while an ^undulation passes 

 through the water, after the wave has passed, the water 

 particles are still where they were and have not received 

 any movement in a horizontal direction. Actually the 

 movement of the water particles is a circular one, backward 

 and upward on the lower half of the wave front, then forward 

 and upward to the summit of the crest, forward and down- 



