60 D. Prain — Flora of Narcondam and Barren Island. [No. 2, 



volcanoes did not carry the chain beyond Barren Island, bnt Griffith, 

 who in passing Narcondam recognised its volcanic nature, suggested 

 to McClelland that here might be seen a northward extension of the 

 same chain. McClelland not only adopted the suggestion but sought a 

 still further extension to the north, in the mud- volcanoes of Ramri and 

 Cheduba, off the Arracan coast ;* and other writers, such as Daubeny, 

 Scrope, Mrs. Somerville and Mallett f have adopted the same view. 



Ramri and Cheduba lie to the west of a tertiary ridge that composes 

 the Tomah of Arracan, which, in the latitude of Ramri, reaches a 

 height of 4,000 feet. This rauge is continued southward into and 

 beyond the Andaman group. Thus it passes through Diamond Island 

 to the Alguada reef, beyond this, across a channel less than 60 fathoms 

 deep, to Preparis, and again across another of 150 fathoms to the Coco 

 Group, Great Andaman and Little Andaman. It would appear after 

 this to pass to the westward of the Nicobars, though its precise relation- 

 ship to that group has not yet been made clear ; finally it reappears, not 

 in Sumatra, but in a long line of islands — the Nias group — that stretches 

 south-eastward along the western coast of Sumatra. J The line of 

 volcanic activity to which Barren Island and Narcondam presumably 

 belong, lies from Narcondam southwards to the east of this tertiary 

 ridge ; if, therefore, Ramri and Cheduba belong to the same line, we 

 have to believe that, after continuing for the whole length of Sumatra 

 and the Andamans parallel to this ridge, the volcanic line at its nor- 

 thern end, where its activity is weaker than elsewhere, crosses the 

 tertiary formations where they have become thicker and stronger. 

 This is in itself a proposition, the truth of which is so hard to accept, 

 that when Blanford§ suggests that the true northern continuation 

 of the Sunda volcanic range is to be found in the extinct Burmese 

 volcano of Popah, and the extinct Yunnan one of Han-shuen-shan, we 

 realise that he must be right, and are surprised that, after all, Mallet is 

 inclined, in a modified sense, to favour the earlier view.|| The volcanoes 

 of Ramri are of a different type from those of the Sunda Range ; they 

 belong to a series of gas vents, all of the same general character, though 

 none of them so active as the Ramri ones. The Sitakund in Chittagong, 



* McClelland, Journ. As. Soc. Beng., vii., 77. 



t Mallet does this (Eecords of the G-eol. Survey of India, xi., 203) in a different 

 sense from the earlier writers ; they, owing to a want of definiteness in the accounts 

 on which they relied, mistook the " gas " volcanoes of the Arracan Coast for true 

 " steam " volcanoes. 



% Kurz : Journ. As. Soc. Beng., xlv., pt. 2, 105. 



§ Manual of the Geology of India, iii., 725. 



|| Mallet : Memoirs of the Geol. Survey of India, xxi., 253. 



