46 



THE TIDES. 



in foam, and the ocean in a few minutes presents 

 the appearance of a caldron of boiling milk ! Such 

 squalls are extremely dangerous to mariners, and 

 vessels exposed to them are often thrown on their 

 beam-ends, even though all sail has been previously 

 taken in. Generally speaking, however, the im- 

 mediate effect of wind passing either lightly or 

 furiously over the sea is to raise its surface into 

 waves. But these waves, however large they may 

 be, do not affect the waters of the ocean more than 

 a few yards below its surface. The water below 

 their influence is comparatively calm, being affected 

 only by ocean currents. 



The tides of the sea as the two great Sowings 



THE FLOWING TIDE. 



and ebbings of the water every twenty-four hours 

 are called are caused principally by the attractive 



