INDIAN OCEAN. 245 



p. 214) ; it appears also encircled in Captain Owen's chart of 

 Madagascar ; coloured blue. — Great Comoro Island is, as I 

 am informed by Dr. Allan, about 8,000 feet high, and ap- 

 parently volcanic ; it is not regularly encircled ; but reefs 

 of various shapes and dimensions jut out from every head- 

 land on the W., S., and S.E. coasts, inside of which reefs 

 there are channels, often parallel with the shore, with deep 

 water. On the N.W. coasts the reefs appear attached to the 

 shore. The land near the coast is in some places bold, but 

 generally speaking it is flat ; Horsburgh says (vol. i. 

 p. 214), the water is profoundly deep close to the shore, from 

 which expression I presume some parts are without reefs. 

 From this description, I apprehend the reef belongs to the 

 barrier class ; but I have not coloured it, as most of the 

 charts which I have seen represent the reefs round it as very 

 much less extensive than round the other islands of the group. 

 Madagascar. — My information is chiefly derived from the 

 published charts by Captain Owen, and the accounts given by 

 him and by Lieut. Boteler. Commencing at the S.W. ex- 

 tremity of the island : towards the northern part of Star Bank 

 (in lat. 25° S.) the coast for ten miles is fringed by a reef; 

 coloured red. The shore immediately S. of St. Augustiii's 

 Bay appears fringed ; but Tullear Harbour, directly N. of it, 

 is formed by a narrow reef ten miles long, extending parallel 

 to the shore, with from 4 to 10 fathoms within it. If this 

 reef had been more extensive, it must have been classed as a 

 barrier-reef; but as the line of coast falls inwards here, a 

 submarine bank perhaps extends parallel to the shore, which 

 has offered a foundation for the growth of the coral; I have 

 left this part uncoloured. From lat. 22° 16' to 21° 37', the 

 shore is fringed by coral-reefs (see Lieut. Boteler's Narrative, 

 vol. ii. p. 106), less than a mile in width, and with shallow 

 water within. There are outlying coral shoals in several 

 parts of the offing, with about 10 fathoms between them and 

 the shore, and the depth of the sea one mile and a half sea- 



