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94 ON THE GEOLOGY OF FERNANDO NOBONHA. 



believe, the rocks marked on the Admiralty Chart as "the 

 Brothers." The name is not known to the inhabitants, who have 

 given the same appellation to the twin rocks off Sambaquichaba. 

 Passing round the coast, we come next to Cotton-tree Bay, where 

 there is a reef some little way from the shore and covered at high 

 water. On the west corner of the bay is a deposit of reef-rock, 

 100 feet above sea-level and 100 feet in thickness, overlying basalt. 

 No more is met with till Tobacco Point, where is a large deposit 

 of raised reef. 



The living reef at the present day occurs on the islands in a 

 number of spots, not continuously, but here and there, sometimes 

 in the form of short spits, at others covering large extents of the 

 sea-bottom. In Rat Island it covers the whole of the western 

 corner and attains considerable thickness in parts ; but the only 

 living reef is on the south-west angle, where the sea beats 

 violently from the south. The rest of the corner consists of a 

 deposit of dead reef, with a layer of guano from 4 to 10 metres 

 thick overlying it. In one spot it overlies a beach of basalt- 

 pebbles of large size, which is continuous with a similar uncovered 

 beach to the north. The dead reef projects in the form of 

 weathered pinnacles all over this part of Bat Island and also in 

 Booby Island, which is evidently a continuation of the same reef 

 broken through after being raised above sea-level by the waves. 

 The reef here rings to the hammer, and is very hard and compact; 

 it appears to have much sand in it. Egg Island is apparently 

 also a continuation of this reef. 



The island known as San Jose, or Platform Island, is composed 

 of a basis of basalt, still connected with the mainland by a band 

 of basalt, forming a kind of ridge of pebbles, bare at very low 

 tides. It appears to be the remains of a large promontory, of 

 which the Morro do Chapeo forms a part. It is a basalt rock 

 about 90 feet high, is capped with reef about 6 feet thick, and 

 containing more distinguishable animal-remains than most of the 

 raised reef. The reef on Morro do Chapeo is about the same 

 height above sea-level (about 10 feet) as that on Egg Island, and 

 very much lower than that on San Jose. Passing along the north 

 side of the Main Island, there is no reef till we reach Chaloupe 

 Bay, the shore consisting of large basalt pebbles, with very large 

 .crystals of olivine and enstatite at the extreme eastern point, and 

 sand from San Antonio Bay to Chaloupe Bay. In Chaloupe Bay 

 there is a large patch of living coral-reef, extending the whole 

 length of the bay, and entirely covered at high water. 







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