174 



Sketch of the Geology of the 



obtained, among innumerable minerals, which may be observed scat- 

 tered about on the surface of the island, very frequently covered with 

 a blue coating, produced by the presence of iron. Besides mesolite I 

 observed chalcedony, agates, rock-crystal, calcareous spar, and heu- 

 landite. 



The south-east point of the small hill consists of craggy rocks of 

 porphyry, affording, in their numerous recesses, abundance of hiding 

 places for lizards and serpents, especially the cobra de capello, which 

 is extremely frequent in these islands. The clefts also afford good 

 habitats for the fern Gymnogramma chylomelanos, and. the Asparagus 

 sarmentosus. 



The large Caranja hill is similar in its conformation to the smaller 

 bill, and is crowned by the ruins of an old fort, which was a place of 

 considerable note, when Europeans first settled on this coast. 



At low water the island is connected with the continent, the inter- 

 vening valley being quite green, and studded with a few pools of water. 

 The vale which separates the two hills, and divides the island into two 

 parts, is covered with palm trees, amid which are situated cottages and 

 rich gardens, at a small elevation above the level of the sea. 



General Observations. 



In the course of the preceding remarks it appears that, on the con- 

 tinent and along the coasts of the different islands, the soundings- do 

 not deepen suddenly, but that the water at the shore is shallow, and 

 that it gradually increases in depth in proportion as we recede from 

 the land. The same remark applies to the whole coast, from the 

 Persian Gulf to Cape Comorin, and it is on a careful attention to the 

 depth of water and the nature of the bottom, that navigators in stormy 

 weather must depend. In the latitude of Bombay this remarkable sub- 

 marine portion of land which can thus be reached with the lead, attains 

 an additional degree of breadth, jutting out to a greater extent into the 

 Arabian sea, and, from its occupying such a considerable space, and 

 affording good fishing ground, although it can only be considered as an 

 expansion of the shoal water along the coast, it has been termed the 

 Bank of Soundings. The deposit generally obtained in the bottom of 

 the harbour, and on this bank near the coast, consists of a blue clay of 

 a stiff nature, and is, therefore, serviceable by affording good holding 

 ground for anchors. A section, representing the relative situations of 

 the sea and the Bank of Soundings, will explain the subject more clear- 

 ly than can be expressed by detailed descriptions. The horizontal line 

 (See plate 18), represents the sea level, and the inclined one the bot- 

 tom of the ocean, which is here shewn to be a gradual descent 

 from the summit of the high land. By sounding regularly, we dis- 



