and of the East African Mainland. 41 



Recent Coral Growths. 



Cases of possible embryo reefs have been given in my account 

 of Zanzibar. Two areas of luxuriantly growing coral remain to be 

 described, viz. the west side of Ras 1 Kegomache, the northern- 

 most point of Pemba, and the islets of Pungutiachi and Pungutiayu 

 to the S.W. of Wasin. 



Ras Kegomache, like all the west coast of Pemba, is extremely 

 steep, 40 fathoms being found at a distance of a quarter of 

 a mile. The steamer anchored very near to the reef edge in 

 15 fathoms. Even at this depth the bottom is dimly visible, in 

 marked contrast to Zanzibar, where the impurity of the water 

 hides everything below about five fathoms. The reef edge is 

 a steep bank of growing coral. Its surface, level with the water 

 at low spring tides, is one-third of a mile broad, without any 

 channel, and composed for the greater part of recently dead and 

 still growing corals, old rock appearing only near shore. A little 

 to the south this coral bank encloses holes several fathoms deep, 

 floored with white sand, looking blue through the clear water, or 

 it breaks up into isolated mounds. The state of things is exactly 

 as that described by Dana for coral growths in the sheltered water 

 inside reefs. A typical coral reef is a very different thing to 

 a mere mass of corals lying in mounds as here, where neither 

 formation of reef conglomerate nor reef edge with its characteristic 

 fissures occurs. 



The rock flats of Pungutiayu and Pungutiachi Islets, which 

 are exposed to the open ocean, are at a level of a few feet above 

 low tide, their edges sloping down to the surface of its fringe 

 a few yards wide of recent coral which is at this level. The edge 

 of the reef is rather irregular, fissures appearing as the breakers 

 recede, and pinnacles of coral occur just beyond it. 



The importance of the proximity of clear and deep water to coral 

 growth is strikingly exemplified in these two cases. In Zanzibar 

 channel abundant coral growth extends only to a depth of five 

 fathoms or less, which is about the depth to which one can see 

 the bottom dimly. Only at Ras Kegomache is the bottom seen 

 at a depth of fifteen fathoms (the limit of the visible zone about 

 the Pacific atolls 2 ), and here the coral extends, in greater luxuriance 

 than I have seen elsewhere in East Africa, to a depth of at least 

 ten fathoms, and in isolated clumps to fifteen, as evidenced by the 

 occasional fouling of the steamer's anchor. Immediately to the 

 north of Ras Kegomache but a few hundred yards away from 



1 Ras, Arabic — Cape or Point. 



2 J. Stanley Gardiner, loc. clt. 



