164 



Sketch of the Geology of the 



[Jan. 



nearly three miles in length, assisting, with the aid of Tull Reef, in ren- 

 dering the mouth of the harbour extremely narrow, for, if we deduct these 

 obstructions to navigation, its span is nqt above four miles, although 

 the distance from Coulaba to the nearest point of the continent equals 

 seven miles. 



The Coulaba Reef has been termed, from its forked figure, the Prongs , 

 and appears to consist of the general rock, in a highly indurated form. 

 The same series occurs at the New Bunder, by the Apollo Gate, where 

 the amygdaloid appears to lie over the porphyry, which is is very hard 

 when first exposed, and is employed as a building material. The New 

 Bunder is formed of it ; but notwithstanding the excellent quality of the 

 stone for enduring the effects of aqueous friction, it is remarkable that 

 an effectual plan has not been fallen upon to render the building of the 

 jutty durable, as it is continually undergoing displacement from the 

 action of the tide. The utility of the Bunder cannot be disputed for the 

 numerous ships which annually increase in frequenting this excellent 

 port, and the situation of this quay, from its being exterior to the fort, 

 is very important, and is perhaps safer than the old Bunder during the 

 height of the moonsoon. 



To the north of the town the surface begins to rise gradually until 

 the small eminence of Mazagon is formed. Beyond it are Parall and. 

 Oblong Hills, all preserving a rounded outline, thinly sprinkled with 

 cocoa-nut trees (Cocos nucifera), and affording some pasture land. At 

 Baboola, a tank has been cut out of the soljd rock, supplied with a 

 broad flight of steps, to enable the inhabitants to have free access to 

 the water, which they employ for all purposes. It is from similar 

 reservoirs that the principal supplies of water for domestic purposes 

 are obtained, and for the use of the crews of ships visiting the harbour. 



As much discussion has taken place with regard to the influence 

 which water procured from such sources may have upon the health of 

 seamen, by affecting the alimentary canal, and, as the solution of the 

 difficulties of the inquiry are very closely connected with the geological 

 nature of the country, a few words upon the subject may not be out of 

 place here. The whole of the soil w 7 hich covers the island being ex- 

 tremely thin, it is obvious that the bottoms of the tanks, which are 

 several feet below the level of the surrounding surface, must consist of 

 solid rocks, and the margins being fortified with artificial building, we 

 see that the w r ater can have little opportunity of acting upon the soft 

 soil, so as to produce a mixture of the earthy particles, and hence, 

 that the substances of a saline nature in solution must derive their 

 origin from the disintegrated rocky mass. A muddiness, however, 

 generally exists in these waters, which appears to be produced by the 

 agitation excited by the natives entering for the purpose of carrying 

 off the water, and for bathing ; but the proportion of mechanical mix- 

 ture thus occasioned does not necessarily exist in general to any greatly 

 appreciable amount, because,, when the cause of excitement is removed, 



