3B2 THE BOTTOM OF THE SEA. 



proof that the land, at tliat particular spot, is rising. 

 If the sea be gaining ou the land, we may be assured 

 that the soil is sinking. 



On any coast terminated abruptly by a high cliff, 

 we may perceive above high water-mark an easily 

 distinguishable line. The waves disintegrate the 

 rocks. They are aided in their work by animals, 

 of which we have spoken on a previous page. The 

 pholades and other stone-borers are impelled by 

 their instincts to select for their abode the line of 

 demarcation between the two elements, where the 

 air and water may be said to strive in perpetual con- 

 flict. These boring animals cannot lemain con- 

 tinually submerged, but the presence of water is in- 

 dispensable to their existence. The clifls against 

 which the waves dash are better suited to their 

 existence than any other situation. Wherever we 

 find that these animals have established their abode, 

 there must have been at one time the seashore. If 

 the sea gains on the land, the colonies of pholades 

 advance higher with the waves ; if the sea retires 

 before a rising contin.ent, the pholades follow in its 

 retreat. 



Where the waves die away on a beach only 

 slightly inclined, a coast-line is formed of I'ounded 

 pebbles and rubbish, across which the waves only 

 [)ass dui'ing great storms. This line defines the 



