311 Prof. BayJey Balfour on the Island of Socotra, dr. [April 20, 



mncli seamed and fractured by volcanic outbursts — tlie sandstone of 

 which we have such a large development in Xubia. This sea sub- 

 sequently deepened, allowing the formation of the shales, which now 

 constitute the argillite of the island. During the Permian, Socotra 

 may have been a land surface, forming part of the great mass of land 

 which probably existed in the region at that epoch. In early and 

 middle Tertiary times, when the Indian peninsula was an island, 

 and the sea which stretched into Europe washed the base of the 

 Himalayan hills, Socotra was probably under water, and the great 

 mass of its limestone was deposited ; but it is quite possible that at 

 this epoch its higher peaks were still above water. Thereafter it 

 gradually rose, undergoing violent volcanic disturbance, and again 

 possibly became part of the mainland, though it is likely for only a 

 short period, and subsequently it reverted to its insular condition, in 

 which state it has remained. 



An island, then, from Tertiary times, the various denuding agents 

 have during that time sculptui-ed its surface in the fantastic manner 

 we see at the present day ; and the fauna and flora have lost many 

 of the old types which linked them with their primitive stock, 

 retaining, however, some few as records of their origination, and at 

 the same time have developed new and replacing forms, which are in 

 their turn undergoing modification. 



[B. B.] 



