Mr Crossland, The Coral Reefs of Zanzibar. 
493 
The Coral Reefs of Zanzibar. By Cyril Crossland, B.A., 
Clare College. 
[ Read 19 May 1902.] 
Introduction. 
My opportunity for observing the facts upon which this 
paper is based arose from the enthusiasm for science of Sir 
Charles Eliot, K.C.M.G., H.M. Consul-General at Zanzibar, and 
Commissioner for the East African Protectorate, who took me 
out to assist in his work on Opisthobranch Mollusca. To our 
disappointment we found the neighbourhood of Zanzibar a poor 
collecting ground. For nearly a year I made my head-quarters 
on the east side of the island at Chuaka. At low spring tides 
Chuaka Bay is a wfide expanse of bare sand, and though 
I found these banks extremely rich in both Polychaeta and 
Opisthobranchiata, I often wished to be nearer deep water for 
dredging, and to see the more typical conditions of life on the 
open coast. At Sir Charles Eliot’s suggestion I first visited the 
Mnemba reef, and that journey made me feel the fascination of 
boat travel so that afterwards I undertook several other excursions. 
In this way I gained a knowledge of the reefs from Ras Nungwe, 
the northernmost point of the island, to Ras Mkundnchi 1 , which is 
the south-east corner. 
I wish to express my thanks to the Zanzibar Government for 
the loan of a boat during my stay. 
Physical Conditions, Seasons. 
The tides rise 15 feet at springs, 10 feet at neaps. On the 
east coast there is always a northerly current, varying from two 
to four miles an hour in the south-west monsoon, and from one to 
three in the north-east. This runs through the channel between 
Zanzibar and Pemba ‘with great velocity’ 2 . It is the result of 
1 My authority for place-names is T. J. Last, Esq., Slavery Commissioner of the 
Zanzibar Government, whose knowledge of the language and of the island exceeds 
that of any other resident. 
2 The African pilot. 
