VALUE OF TIDES. 49 



torrent, and any one caught by them on the shore 

 would be overtaken and drowned before he could 

 gain the dry land. In the open sea they rise and 

 fall to an elevation of little more than three or 

 four feet. 



The value of the tides is unspeakable. They 

 sweep from our shores pollution of every kind, purify 

 our rivers and estuaries, and are productive of fresh- 

 ness and health all round the world. 



(451) 



