INDIAN OCEAN. 
253 
Augustin'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 seaward, is only 
about 30 fathoms. The part above specified is engraved on a 
large scale ; and as in the charts on rather a smaller scale 
the same fringe of reef extends as far as lat. 23° 15', I 
have coloured the whole of this part of the coast red. The 
islands of Juan de Nova (in lat. 17° S.) appear in the charts 
on a large scale to be fringed, but I have not been able to 
ascertain whether the reefs are of coral ; uncoloured. The 
main part of the west coast appears to be low, with outlying 
sand banks, which Lieut. Boteler (vol. ii. p. 106) says, ‘ are 
faced on the edge of deep water by a line of sharp-pointed 
coral-rocks.’ Nevertheless I have not coloured this part, 
as I cannot make out by the charts that the coast itself is 
fringed. The headlands of Narrencla and Passandava Bays 
(14° 40') and the islands in front of Badama harbour are 
presented in the plans as regularly fringed, and have 
accordingly been coloured red. With respect to the East 
Coast of Madagascar, Dr. Allan informs me, that the whole 
line of coast, from Tamatave hi 18° 12' to G. Amber at the 
extreme northern point of the island, is bordered by coral- 
reefs. The land is low, uneven, and gradually rises from 
the coast. From Captain Owen’s charts, the existence of 
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