30 THE TIDES. 



Ocean, partly running round Australia, partly 

 finding its way through the numerous straits of 

 the Indian Archipelago. The Atlantic Ocean, 

 severed almost entirely from the great ocean by 

 the far-stretching continent of America, receives 

 now most of the remaining force of the wave, as, 

 turning the southern point of Africa, it presses 

 onwards to the north, until it is lost in the Arctic 

 Sea. It is to this that we chiefly owe the tides 

 of our European and American coasts. 



Now the tide-wave requires time for its develop- 

 ment, and therefore, at the place of its origin, is 

 not completed till after the moon has passed the 

 meridian. Moreover in all smaller seas and arms 

 of the sea, in which tides occur, these tides must 

 be due to the progress of the wave derived from 

 the Pacific Ocean ; and the obstacles which oppose 

 its advance, and by which it is at last arrested, 

 vary very much according to the form of the coasts, 

 to the width and depth of the sea, and to the 

 number and size of the islands that it meets with. 

 For these reasons the tides, that visit the coasts 

 of Europe, must be retarded, so as to occur con- 

 siderably later than the cause from which they 

 arise. Thus for instance the tide-wave requires 

 (according to the reckoning of Whewell) fourteen 

 or fifteen hours to travel from the southern end of 

 Africa to the coasts of Spain, of Erance and of Ire- 

 land. And then, on account of the increased resist- 



