242 APPENDIX. 



rivers) to deepen their muddy beds. When describing in 

 the chapter on fringing-reefs, those of Mauritius, I have 

 given my reasons for believing that the shoal spaces 

 within reefs of this kind, must, in many instances, have 

 been deepened. However this may be, as several parts of 

 this line of coast are undoubtedly fringed by living reefs, 

 I have coloured it red. — Maleenda (3 20' S.). In the 

 plan of the harbour, the south headland appears fringed ; 

 and in Owen's chart on a larger scale, the reefs are seen to 

 extend nearly thirty miles southward; coloured red. — - 

 Mombas (4 5' S.). The island which forms the harbour, 

 "is surrounded by cliffs of madrepore, capable of being 

 rendered almost impregnable " (Owen's Nar., vol. i. p. 412). 

 The shore of the mainland, N. and S. of the harbour, is 

 most regularly fringed by a coral-reef at a distance from half 

 a mile to one mile and a quarter from the land ; within the 

 reef the depth is from nine to fifteen feet ; outside the reef 

 the depth at rather less than half a mile is thirty fathoms. 

 From the charts it appears that a space about thirty-six 

 miles in length, is here fringed ; coloured red. — Pemba 

 (5 S.) is an isld. of coral-formation, level, and about 200 

 feet in height (Owen's Nar.^ vol. i. p. 425) ; it is 35 miles 

 long, and is separated from the mainland by a deep sea. 

 The outer coast is represented in the chart as regularly 

 fringed; coloured red. The mainland in front of Pemba 

 is likewise fringed ; but there also appear to be some out- 

 lying reefs with deep water between them and the shore. 

 I do not understand their structure, either from the charts 

 or the description, therefore have not coloured them. — 

 Zanzibar resembles Pemba in most respects ; its southern 

 half on the western side and the neighbouring islets are 

 fringed ; coloured red. On the mainland, a little S. of 

 Zanzibar, there are some banks parallel to the coast, which 



