260 APPENDIX. 



parts a worn-down promontory, partially coated and fringed 

 by reefs : I lean, however, to the probability of its being 

 a barrier-reef, produced by subsidence. To add to my 

 doubts, immediately on the outside of this barrier-like reef, 

 Turneffe A Lighthouse, and Glover reefs are situated, and 

 these reefs have so completely the form of atolls, that if 

 they had occurred in the Pacific, I should not have hesi- 

 tated about colouring them blue. Turnejfe Reef seems 

 almost entirely filled up with low mud islets ; and the 

 depth within the other two reefs is only from one to three 

 fathoms. From this circumstance and from their similarity 

 in form, structure, and relative position, both to the bank 

 called Northern Triangles, on which there is an islet be- 

 tween 70 and 80 feet, and to Cozu??iel Island, the level 

 surface of which is likewise between 70 and 80 feet in 

 height, I consider it more probable that the three foregoing 

 banks are the worn-down bases of upheaved shoals, fringed 

 with corals, than that they are true atolls, wholly produced 

 by the growth of coral during subsidence; left uncoloured. 



In front of the eastern Mosquito coast, there are between 

 lat. 12 and 16 some extensive banks (already mentioned, 

 p. 253), with high islands rising from their centres; and 

 there are other banks wholly submerged, both of which 

 kinds of banks are bordered, near their windward margins, 

 by crescent-shaped coral-reefs. But it can hardly be 

 doubted, as was observed in the preliminary remarks, that 

 these banks owe their origin, like the great bank extending 

 from the Mosquito promontory, almost entirely to the accu- 

 mulation of sediment, and not to the growth of corals; 

 hence I have not coloured them. 



Cayman Island : this island appears in the charts to be 

 fringed ; and Capt. B. Allen informs me that the reefs 

 extend about a mile from the shore, and have only from 



