248 SEA AND LAND 



These species abound in many harbors which are visited 

 by warm waters, and often bring about the formation of a 

 lime ooze composed of such finely divided matter that the 

 material is readily swept about by the tidal currents. De- 

 posits formed of the remains of these creatures abound in 

 the regions of coral reefs. In such reef-bordered shores the 

 species of coral which dwell within the lagoon are very effective 

 agents in shoaling the waters which they inhabit. This result 

 is, however, combined with that which is effected by a host 

 of other orsfanic forms. 



Before taking leave of the interesting phenomena exhibited 

 by the organic deposits of the coast-lines it is well to con- 

 sider them in a somewhat more general manner than we 

 have hitherto done. In the first place we should notice 

 that the amount of these contributions made to the sea-floor 

 and the importance which they have to the life of man are 

 alike singularly great. Although the ocean bottom is almost 

 everywhere receiving contributions of organic sediment, the 

 quantity of this material which is laid down next the shore 

 is far greater than that deposited beneath the deeper seas. 

 The reasons for this accentuation of the coastal deposits 

 which are laid down by animals and plants is easily per- 

 ceived. It is due in part to the large quantities of material 

 fitted to be the food of animals and plants which is con- 

 veyed from the land to the sea by streams of fresh water. 

 In part it is contributed by the action of the waves, which 

 are constantly at work grinding up organic and inorganic 

 material and diffusing it in a way to serve the needs of 

 living beings. Still farther along the shallows next the 

 shore the light of the sun penetrates through the water to 

 the bottom and there stimulates the growth of a host of species 



