58 D. Praia — Flora of Narcondam and Barren Island. [No. 2, 



through the rock ; along this line the soundings show a rather sharp 

 ridge with relatively shallower sonndings for the whole length of 

 the hank ; this line, it is hardly necessary to repeat, is that on which 

 both Narcondani and Barren Island also show their shallowest sound- 

 ings, while the axes of all three islands indicated by this direction form 

 very nearly a continuous straight line. 



The nature of the bottom on this bank is only mentioned in the case 

 of one sounding ; this depth, 25 fathoms, gives, as might be expected, 

 coral: it would be interesting to ascertain whether the subaerial portion, 

 Flat Rock itself, is part of a raised coral reef, or a remnant of an origin- 

 ally larger island of volcanic structure. Raised coral reefs occur in the 

 Andamans to the west, and in the Nicobars to the south ; it may there- 

 fore be anticipated that here it will be found that the subaerial portion 

 of the bank is weathered coral ; at the same time it would be more satis- 

 factory to have the question settled by a visit to the rock. Reasoning 

 from analogy, however, there is little doubt that the basis of this coral 

 bank is a submarine volcanic peak, and that it forms but one of a series 

 to which the others also belong. 



Our knowledge of the bottom-contour of the Andaman Sea is not 

 so satisfactory as is that of the Sea of Bengal. English geographers 

 ecive no attention to the point ; German geographers have mapped the 

 sea somewhat hastily and from rather meagre data. Thus Berghaus 

 indicates by the contour lines in a map of "Heights and Depths"* 

 that a deep gap, connecting the Sea of Bengal and the Andaman Sea, 

 exists between Achin Head in Sumatra and the Nicobars. It has how- 

 ever long been known that the ridge in this channel carries only 760 

 fathoms of water. In a larger map f Berghaus shows deep water as 

 overlying not only the ridge between the Nicobars and Sumatra, but 

 also over that between the Andamans and Nicobars and, what is quite 

 unaccountable, between Preparis and the Coco Group ; this last channel 

 has long been known to carry no more than 150 fathoms. As regards 

 that between Little Andaman and the Nicobars, Carpenter had, on 

 grounds of temperature, predicted what Hoskyn has since shown to be 

 true, that the ridge under it could carry at the utmost 740 fathoms ; its 

 actual depth is 736 fathoms. In this map also two soundings are shown 

 in the meridian of Lon. 96° 10' E., one of them in Lat. 11° 35' N., for 



* Stieler's Hand Atlas, Sheet 8, dated 1878. 



f Stieler's Hand Atlas, Sheet 67, dated 1881 and revised to 1884; scale 1: 

 12,500,000. Perhaps the contour line in this map means the 100 fathom line ; this 

 would explain the shading in the straits mentioned. If so, it is too far from land, 

 and coincides with the 1000 fathom line rather than the 100 fathom one, 



