chap. ii. Si. Paul's Rocks. 39 



birds' dung, I found a great quantity of a brown, 

 arborescent substance adhering to some trap-rock. In 

 its arborescent form, this substance singularly resembles 

 some of the branched species of Nullipora. Under the 

 blowpipe, it behaves like the specimens from Ascension ; 

 but it is less hard and glossy, and the surface has not 

 the shrunk appearanca 



