DIFFERENT FORMATION OF SEA-COASTS. 5 



roams along the - coasts of ocean from zone to zone ! what 

 changes, as it wanders from the palm-girt coral island of the 



Beeony Head. 



tropical seas to the melancholy strands where, verging towards 

 the poles, all vegetable life expires ! and how magnificently grand 

 does the idea of ocean swell out in our imagination, when we 

 consider that its various shores witness at one and the same 

 time the rising and the setting of the sun, the darkness of night 

 and the full blaze of day, the rigour of winter and the smiling 

 cheerfulness of spring ! 



The different formation of sea-coasts has necessarily a great 

 influence on commercial intercourse. Bold mural coasts, rising 

 precipitously from the deep sea, generally possess the best 

 harbours. Eocky shores also afford many good ports, but 

 most frequently only for smaller vessels, and of difficult access, 

 on account of the many isolated cliffs and reefs which charac- 

 terise this species of coast formation. 



In places where high lands reach down to the coast, the im- 

 mediate depth of the sea is proportionably great ; but wherever 

 the surface rises gently landwards, the sea-bed continues with a 

 corresponding slope downwards. On these flat coasts the tides 

 roll over a sandy or shingly beach ; and here the aid of human 

 industry is frequently required to create artificial ports, or to 

 prevent those already existing from being choked with sand. 



On many flat coasts the drift-sand has raised dunes, wearying 



