FORM ATI OX. 



139 



to south. Into this basin fall sundry small 

 streams, the Mohayra and others, which are lost 

 through the crevices and caverns, and in the 

 cracks and fissures of the grit. There are 

 other drains, forming, after heavy downfalls, 

 swamps and marshes, whence partly the great 

 insalubrity of the interior. The western part of 

 Zanzibar, with its wealth of evergreen vegetation, 

 appears by far the most fertile. It is a meri- 

 dional band of red clay and sandy hills, running 

 parallel with the corallines of the eastern coast. 

 Here are the most elevated grounds. I found 

 the royal plantation Sebbe or Izimbane, 400 feet 

 (b.p.) above sea-level, or a little higher than the 

 Bermudas. The least productive parts are those 

 covered with dark clay. Heavy rains deposit 

 arenaceous matter upon the surface, and the 

 black humus disappears. On this side of the 

 island also many streamlets discharge into the 

 sea, bearing at their mouths mangrove beds, 

 whose miasmas cause agues, dysenteries, diar- 

 rhoeas, and deadly fevers. 



The rule established by Hampier and quoted 

 by Humboldt directs us to expect great depth 

 near a coast formed by high perpendicular moun- 

 tains. Here, as in the rest of the Zanzibarian 

 archipelago, the maritime line, unlike the west 



