346 



On Tidal Currents in the Ocean. 



[Feb. 2, 



therefore "be little doubt that in this case we have a submarine bank 

 which is in vigorous growth towards the surface, and which has been 

 in existence long enough to have risen through a height of about 300 

 fathoms or 1800 feet. I have little doubt that in a large number of 

 the coral islands of the Pacific, the intermediate platform between 

 the tropical reef-building coral and the volcanic peak, plateau, and 

 ridge, which most probably form the foundation, is formed by these 

 deep-sea corals largely assisted by annelids, especially Serpulae, which 

 secrete calcareous tubes. The tidal currents assist their growth both 

 by bringing the animals nourishment and by removing light debris 

 which might choke them. 



Diagram showing the resultant currents due to the composition of a constant 

 current, OP, with a tidal current, OT, OT/ 



