264 APPENDIX. 



tained by boring, that these submerged banks consisted of 

 madreporitic rocks, covered in many parts by thin layers of 

 mud or sand. From this fact, and especially from the struc- 

 ture of the narrow breaches, these banks were probably formed 

 by living reefs, which fringed the shores of the island, and 

 once reached the surface. From some of these submerged 

 banks reefs of living coral still rise abruptly, either in small 

 detached patches, or in lines parallel to, but some way within, 

 the margin. Besides the above banks which skirt the shores 

 of the island, there is on the eastern side a range of linear 

 banks, similarly constituted, 20 miles in length, extending 

 parallel to the coast-line, and separated from it by a space 

 between two and four miles in width, and from 5 to 15 

 fathoms in depth. From this range of detached banks, some 

 linear reefs of living coral likewise rise abruptly ; and if they 

 had been of greater length (for they do not front more than a 

 sixth part of the circumference of the island) they would ne- 

 cessarily from their position have been coloured as barrier- 

 reefs ; as the case stands, they are left uncoloured. 



Flokida. — An account of the reefs on this coast, together 

 with references to various authorities, will be found in Pro- 

 fessor Dana's work on Corals and Coral Islands, 1872, p. 204. 



The Bermuda Islands have been carefully described by 

 Lieut. Nelson, in an excellent memoir in the Geol. Transac- 

 tions (vol. v. part i. p. 108). In the form of the bank or reef, 

 on one side of which the islands stand, there is a. close general 

 resemblance to an atoll ; but in the following respects there is 

 a considerable difference, — first, in the margin of the reef not 

 forming (as I have been informed by Mr. Chaffers, R.N.) a 

 flat, solid surface, which is laid bare at low water ; secondly, 

 in the water gradually shoaling for nearly a mile and a half in 

 width round the entire reef, as may be seen in Captain Hurd's 

 chart ; and thirdly, in the size, height, and extraordinary 

 form of the islands, which present little resemblance to the 

 long, narrow, simple islets, seldom exceeding half a mile in 



