J. i). Dana, Esq., on Coral Reefs and Islands, 225 



singularly tenacious of life< and ready to sprout Anew on my 

 rock where they may find quiet long enough to give them- 

 selves again a firm attachment. 



But it should be observed, that the sea would have far less 

 effect upon the slender forms characterising many zoophytes, 

 among which the water finds free passage, than on the mas- 

 sive rock, against whose sides a large volume may drive un- 

 broken. Moreover, much the greater part of the strength 

 of the ocean is exerted near tide level, where it rises in 

 breakers, which plunge against the shores. Yet, owing to 

 the many nooks and recesses deep among the corals, the ra- 

 pidly-moving waters, during the heavier swells, must pro- 

 duce whirling eddies of considerable force, tending to uproot 

 or break the coral clumps. These disrupting and transport- 

 ing effects will be less and less as we recede from the shores ; 

 yet all coral depths must experience them in some degree. 



There is another process going on over the coral field, 

 somewhat analogous to vegetable decay, though still very 

 different. Zoophytes have been described as ever dying 

 while living. The dead portions have the surface much 

 smoothed, or deprived of the roughening points which belong 

 to the living coral, and the cells are sometimes half obli- 

 terated, or the delicate lamellae worn away. This may be 

 viewed as one source of fine coral particles ; and as the pro- 

 cess is constantly going on, it is not altogether unimportant. 

 This material is in a fit condition to enter into solution, and 

 it cannot be doubted that the water receives lime from this 

 source, which is afterwards yielded to the reef. 



In the Alcyonia family, which includes semi-fleshy corals, 

 and the Gorgonise, the lime is often scattered through the 

 polyps in granules ; and the process of death sets those cal- 

 careous grains free, which are constantly added to the coral 

 sands. The same process has been supposed to take place 

 in the more common reef corals, the Madrepores and As- 

 trseas, and it is possible that this may be to some extent the 

 case. Yet it would seem, from facts observed, that after the 

 secretion has begun within the polyp, the secretion of lime 

 going on takes place against the portions already formed, 

 and in direct union with them, and not as granules to be 

 afterwards cemented. 



VOL. LI I. NO. CIV. — APRIL 1852. P 



