106 KATE OF GROWTH. Ch. IV. 



of coral two feet in thickness, which it required great 

 force to remove when the vessel was docked : it was 

 not ascertained to what order this coral belonged. 1 

 This fact in some degree corroborates the result of 

 Dr. Allan's experiments. The case of the schooner- 

 channel, choked up with coral in an interval of less 

 than ten years, in the lagoon of Keeling atoll, should 

 be here borne in mind. We may also infer, from 

 the trouble which the inhabitants of the Maldiva 

 atolls take to root out, as they express it, the coral- 



1 Mr. Stutchbury (West of England Journal, No. I. p. 50) has de- 

 scribed a specimen of Agaricia, ' weighing 2 lbs. 9 oz., which surrounds 

 a species of oyster, whose age could not be more than two years, and 

 yet is completely enveloped by this dense coral.' I presume that the 

 oyster was living when the specimen was procured ; otherwise the fact 

 tells nothing. Mr. Stutchbury also mentions an anchor, which had 

 become entirely encrusted with coral in fifty years ; other cases, how- 

 ever, are recorded of anchors having long remained amidst coral-reefs 

 without having become coated. The anchor of the Beagle, in 1832, 

 after having been down exactly one month at Eio de Janeiro, was so 

 thickly coated by two species of Tubularia, that large spaces of the iron 

 were entirely concealed; the tufts of this horny zoophyte were between 

 two and three inches in length. Spallanzani states (Travels, Eng. 

 Translat. vol. iv. p. 313) that in the Mediterranean, the red coral of 

 commerce is usually dredged every ten years, during which time it 

 grows to a height of one foot. It grows, however, at different 

 rates in different places. It has been erroneously attempted to 

 compute the rate of growth of a reef, from the fact mentioned by 

 Captain Beechey of the Chama gigas being embedded in coral rock. 

 But it should be remembered, that some species of this genus invariably 

 live, both whilst young and old, in cavities, which the animal has the 

 power of enlarging with its growth. I saw many of these shells thus 

 embedded in the outer ' flat ' of Keeling atoll, which is composed of 

 dead rock ; and therefore the cavities in this case had no relation 

 whatever to the growth of coral. M. Lesson, also, speaking of this 

 shell (Partie Zoolog., Voyage de la Coquille). has remarked, ' que con- 

 stamment ses valves etaient engages completement dans la masse des 

 Madrepores.' 



