RA TE OF GRO WTH OF CORAL REEFS. 



217 



occur in the dead rock — generally where there are no growing 

 corals, except rarely some small tufts. If they indicate any- 



Scale of 5oo*meters 



thing, it must be the growth of the reef-rock, and not of the 

 corals themselves. But the shore-platform where they are 

 found is not increasing in height ; its elevation above low-tide 



