835.] • Geology of the Bombay Islands. 837 



which is here shewn to be a gradual descent from the sum- 

 mit of the high land. By sounding regularly we discover 

 our distance from the coast, as appears from the following 

 table :— 



10 miles from the coast the soundings are 14 fathoms ; 

 bottom, mud. 



40 do. 40 fms., sand, gravel, and shells of various colours. 



50 do. 45 do. do. 

 160 do. 50 do. do. 

 170 do. 55 do. do. 



We observe, therefore, that soundings extend as far to the 

 westward of Bombay as 2° 50', and that, until the bottom 

 of the ocean begins to ascend, in order to come to the day; 

 the bed consists of sand, mixed with shells, and that then 

 it is formed of mud. An observation with respect to the 

 nature of the shells would be of considerable importance, 

 because it might enable us to decide, whether they are 

 natives of deep water, or belong to the shallower parts of 

 the ocean. 



Two explanations occur, to account for the appearances 

 here described, either, 1st. That the land and ocean have 

 retained their positions relative to each other since the 

 formation of the first, the production of the bank being- 

 similar to the clay deposit round the shore of the island 

 which so lately appeared, and sunk in the Mediterranean ; 

 or 2d., That the harbour of Bombay was formerly a valley, 

 and that the Bank of Soundings was at one time dry ground, 

 both of which have been submersed by the gradual en- 

 croachment of the sea. The most undoubted evidence 

 exists to shew us that this coast has been, even within the 

 range of a few centuries, subjected to violent convulsions 

 from earthquakes 



vol. i. z 



