GROWTH OF REEFS 95 



of the corals. Sand, partially the remains of the above 

 organisms, but largely composed! of the shells of pelagic 

 unicellular organisms (Foraminifera), collects between 

 the corals and helps to solidify the whole structure, 

 while creeping and spreading Lithothamnia form a 

 surface firm enough to resist the mightiest breakers. 

 The relative share of each organism varies in each 

 locality, and is always a matter of interest. 



Let us now trace further the probable fate of our 

 reef before proceeding to controversial theories. Its 

 breadth will depend on the area of the shoal on which 

 it was founded, or on the area within the 30-fathom 

 line round the land. It will be a flat on the surface, 

 with the corals dead on the top or represented only by 

 small colonies of poor growth. The sea will be surging 

 up around, bringing abundant " food " to its face, and 

 here corals will be found growing vigorously as deep 

 as the eye can see, 15 fathoms or more. The rollers 

 will be constantly pounding down on its edges and 

 breaking off colonies, a few of which may be cast upon 

 the surface of the reef to form a boulder zone, but 

 most of which will be washed outwards to bring fresh 

 areas within suitable depths for the reef builders. As 

 this process continues, the reef will be spreading farther 

 and farther seawards, broadening its surface, and 

 making life less and less possible on its inner zone as 

 the animals become more distant from their chief 

 source of food-supply, the open waters of the ocean. 

 This process might continue indefinitely, the rate of 

 outward growth depending on the steepness of the 

 outer slope of the ocean floor. The outgrowth must 

 be assumed to result finally in the (almost universal) 

 gradual slope for about 200 yards to about 40 fathoms, 

 followed by the steep slope, often with an angle of 

 over 40 degrees to about 140 fathoms. At this depth 



