160 



Sketch of the Geology of the 



[Jan. 



A considerable proportion of the remaining part of this bay is occu- 

 pied by Bombay, Caranja, Elephanta, Butcher, Woody, and Cross Is- 

 lands, which, being disposed in a crescentic manner, form the harbour 

 of Bombay, an open and extensive bason 'eight miles in diameter, af- 

 fording good anchoring ground and secure shelter for fleets of ships of 

 the largest burthen. It is these insulated portions of land, that I have 

 designated the Bombay Islands. The appearance presented by these 

 islands is highly picturesque, as they are in many places adorned with 

 thriving woods, which, between the tropics, always produce rich and re- 

 freshing scenery. But, in the Island of Bombay, the present trees ap- 

 pear of recent origin ; for, we learn from older writers that the land was 

 formerly swampy, and afforded no plants or trees worthy of mention. 

 At present the higher parts of Salsette and Caranja are nearly destitute 

 of trees, but they are for the most part thickly clothed with straggling 

 jungle. 



The general contour of these islands corresponds closely with that of 

 the adjacent continent, and far as the latter has been investigated, the 

 formation appears identical. The altitude attained by the rocky masses 

 in these insulated lands is never great, although they are all considera- 

 bly elevated above the level of the ocean. The dark hills of Salsette 

 reach the greatest height, next to them in order come the rugged mass- 

 es of Caranja and Elephanta, but Bombay and the remaining islands 

 approach more nearly the character of plains. 



Before taking a separate view of each of the more considerable of 

 these islands, it seems satisfactory to present' at one view a description 

 of the rocky masses and minerals, which form their essential consti- 

 tuents, and here it may be premised, that the rocks belong all to that 

 class which has been termed trappean, or, theoretically, volcanic, as 

 distinguished from the granitic series, or plutonic rocks. 



1. Basalt, occurring in situ at the ruins of a chapel in Salsette ; co- 

 lour, dark-gray, or blackish, with numerous crystals of olivine and 

 augite interspersed ; fracture, irregular, dull. The upper portion of the 

 ridges in Salsette appears to consist of this rock, or modifications of it. 



2. Black basalt, in Elephanta, often presenting a homogeneous aspect 

 when fractured, but frequently containing minute portions of olivine, 

 sometimes in rounded granules, at other times crystallized ; texture 

 highly indurated. This and the former variety, fuse before the blow 

 pipe per se into a mass, resembling pitchstone. The celebrated figure 

 of the elephant, close to the vilrage of Gallipooti, consists of this rock 

 but it appears to be of limited extent. 



3. Amygdaloid, appearing at the great temple of Elephanta, possess- 

 es a hard wacke basis, containing cavities filled with rock crystal and 

 zeolites, &c, some of which are often met with enclosed in the strong 

 mass in the form of rounded nodules, whose crystalline structure is not 



