296 Dr. R. D. Thomson, on the [April 



ritasque mare litoribus infundit," it is not easy to give a 

 satisfactory explanation, although the latter obviously relate 

 to the pearls of the Indian seas. 



We proceed now to a separate sketch of the islands, in 

 the order of their importance. 



BOMBAY ISLAND. 



The whole island maybe considered as a plain, variegated 

 on the east with considerable undulations, which form the 

 small eminences termed Mazagon, Parell, and Oblong hills. 

 The southern part divides into two necks of land, of which 

 the eastern portion, a low and flat surface, affords the site 

 for the Fort and Dungeree, or the Black Town, and leav- 

 ing an intermediate space called the Esplanade, terminates 

 at Mendam's Point, the commencement of the Coulaba 

 Causeway. The western promontary is considerably elevated, 

 consisting principally of Malabar Hill, which lies near the 

 entry of the harbour, and terminates at Malabar Point. In- 

 cluded between these points, with -a crescentic outline, as 

 between the prongs of a fork lies Back Bay, a considerable 

 portion of water, with a sea communication, occupying a 

 span of 2\ miles, the total mean breadth and length being 

 about 1| and 1 j miles respectively. The water is shoal, 

 having a depth of 2J fathoms in the centre, and contains 

 several sands, sunken rocks, and others exposed- at low 

 water. 



The essential composition of this tract is claystone-por- 

 phyry and amygdaloid, and in some places, as on Malabar 

 Hill, basalt shews itself, each corresponding with the varie- 

 ties described, but seeming to vary with regard to the pro- 

 portion of the bases and the magnitude of the cavities, and 

 consequent quantity of the mineral contents. From Men- 

 dam's Point, a ledge of amygdaloid runs out south-west by 

 south, to form a junction with Coulaba or Old Woman's 

 Island, a flat and rocky mass, thinly covered with soil, 

 which barely conceals the subjacent rocks, bearing every 

 mark of having been at some period a continuous portion 

 of that promontary of the island of Bombay upon which the 

 town is situated. Advantage has been taken of this ledge 

 to form a connecting causeway between the two islands, 

 which is left quite dry at low water, so that a free land 



