CORAL-REEFS. 89 



the heat intense. The total number of species of coral in 

 the circumtropical seas must be very great : in the Red 

 Sea alone, 120 kinds, according to Ehrenberg, 1 have been 

 observed. 



The same author has observed that the recoil of the sea 

 from a steep shore is injurious to the growth of coral, 

 although waves breaking over a bank are not so. Ehrenberg 

 also states, that where there is much sediment, placed so as 

 to be liable to be moved by the waves, there is little or no 

 coral ; and a collection of living specimens placed by him 

 on a sandy shore died in the course of a few days. 2 An 

 experiment, however, will presently be related in which 

 some large masses of living coral increased rapidly in size, 

 after having been secured by stakes on a sandbank. That 

 loose sediment should be injurious to the living polypifers, 

 appears, at first sight, probable ; and accordingly, in sound- 

 ing off Keeling atoll, and (as will hereafter be shown) off 

 Mauritius, the arming of the lead invariably came up clean, 

 where the coral was growing vigorously. This same circum- 

 stance has probably given rise to a strange belief, which, 

 according to Capt. Owen, 3 is general amongst the inhabi- 

 tants of the Maldiva atolls, namely that corals have roots, 

 and therefore that if merely broken down to the surface, 

 they grow up again ; but, if rooted out, they are permanently 

 destroyed. By this means the inhabitants keep their 

 harbours clear; and thus the French Governor of St. 

 Mary's in Madagascar, " cleared out and made a beautiful 

 little port at that place." For it is probable that sand 

 would accumulate in the hollows formed by tearing out the 



1 Ehrenberg, Uber die Natur, etc. , etc. , p. 46. 



2 Ibid., p. 49. 



3 Capt. Owen on the Geography of the Maldiva Islands, Geograph. 

 Jotirnal) vol. ii. p. '&*>. 



