V. Ball — Volcanos of the Bay of Bengal. 17 



northward along the Coast of Arracan, 1 the entire length of the 

 volcanic range is a great deal more." 



Dr. Hochstetter carries the line of elevations which accompanies 

 the zone of volcanic action still further, in an oblique S form, 

 through New Guinea to the north of the Australian continent. "It 

 forms in New Ireland, the Solomon Islands, New Hebrides, and 

 New Zealand, a curve, concave towards the west, the small group 

 of the Macquarie Islands being possibly considered as the extreme 

 southern end of this curve." 



So far as is known, there are no volcanos in either the Nicobar 

 or Andaman Islands. It has been by some supposed that the hill 

 on Bompoka in the Nicobars, and some of the high ground in the 

 Great Nicobar, might be volcanic, but the evidence is rather against 

 than in favour of this view. Igneous rocks (diorite and gabbro) 

 not unfrequently occur, however, in both groups of islands. A 

 statement made in an old account of the Cocos, that the little Coco 

 is formed of volcanic rocks, is, I believe, quite without foundation. 

 The only rocks I observed there were Tertiary sandstones and shales. 



Barren Island, Lat. 12° 17' N. ; Long. 93° 54' E. 



History of the Island derived from Previous Notices. — In the table 

 appended I have given a precis of all that has been published on the 

 subject of Barren Island ; but a few additional remarks, tracing out 

 the way in which certain inaccuracies have arisen, seem to be 

 desirable. 



The first published account was by Captain Blair, in his report 

 on the Andaman Islands, dated 1789. I have not seen the original 

 document, but the account was extracted and reprinted by Lieutenant 

 Colebrooke in the Asiatic Eesearches. 



Captain Blair gave the height of the central cone at " nearly 

 1,800 feet." Were it not also stated, however, that the cone was 

 equal in height to the outer walls of the surrounding part of the 

 island, we might, in consequence of Blair's oft-proved accuracy as 

 an observer, be disposed to believe that at the time of his observa- 

 tion the cone was nearly double its present height. That there has 

 not been a general subsidence of the island to the extent of 800 

 feet is proved by the fact that the base of the cone was then, as it is 

 now, but little raised above the sea-level. Blair himself states that 

 the island may be seen at a distance of twelve leagues in clear 

 weather, which would only require an elevation of about 920 feet. 

 I can only suppose, as an explanation of the difficulty, that Blair 

 took several heights which varied between 800 and 1,000 feet, and 

 that these, by some error, came to be written together as 1,800. 



The angle of inclination of the sides of the cone is stated by Blair 

 to be 32° 17'. 



The sketch by Lieutenant Wales given in Lieutenant Colebrooke's 

 paper, save that it represents an inclination of about 60° for the 

 sides of tbe cone, conveys the best idea of the island of any of the 



1 A very full account of the mud volcanos on this coast has recently been pub- 

 lished by Mr. F. B,. Mallet, F.G.S., Eec. Geol. Survey of India, vol. xi. part ii. p. 188. 



DECADE II. — VOL. VI. — NO. I. 2 



