CHAPTER XI. 



THE SEA AND ITS WORK. 



At Margate, where the estuary of the Thames ends in 

 the North Sea, even a bhnd man could not stand long upon 

 the shingly beach without knowing that the sea was busily 

 at work. Every wave that rolls in from the open ocean 

 hurls the pebbles up the slope of the beach ; and then, as 

 soon as the wave has broken and the water has dispersed, 

 these pebbles come rattling down with the currents that 

 sweep back to sea. The chattel of the beach thus tells us 

 plainly that, as the stones are being dragged up and down, 

 they are constantly knocked against each other ; and, it is 

 evident, that, by such rough usage, all angular fragments of 

 rock will soon have their corners rounded off, and become 

 rubbed into the form of pebbles. As these pebbles are 

 rolled to and fro upon the beach they get worn smaller and 

 smaller, until, at length, they are reduced to the state of sand. 

 Although this sand is at first coarse, it gradually becomes 

 finer and finer, as surely as though it were ground in a mill ; 

 and, ultimately, it is carried out to sea as fine sediment, and 

 laid down upon the ocean-floor. 



On examination of the chalk cliffs, which back the beach, 

 it is easy to see how these suffer by the constant dash of 



