82 
Records of the Geological Survey of India. 
[vot. vi. 
high ground in the great Nicobar might be volcanic, but the evidence is rather against than 
in favor of this view. Plutonic rocks (diorite and gabbro) not unfrequently occur how - 
ever in both islands. A statement made in an old account of the Cocas, that the little Coco 
is formed of volcanic roclcs, is quite without foundation. 
Barren Island, Lat. 12° 17', Long. 93° 54'. 
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 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, It has served for many years as the text 
upon which the descriptions published in various Geological Manuals have been founded. 
Captain Blair gave the height of the central cone at nearly 1,800 feet, and the angle of 
the slope at 32° 17'. Were it not stated that the cone was equal in height to the outer walls 
of the surrounding part of the island, we might, in consequence of Blairs’ oft proved 
accuracy as an observer, be disposed to believe that at the time of his observation 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 it may be seen at a dis¬ 
tance 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 those, by some error, came to be 
written together as 1,800. 
The angle of inclination of the sides of the cone is given by Blair at 32" 17'. This 
nearly corresponds with the mean of my observations, which ranged between 32° and 
35°. These angles also agree with those on a photograph which I possess. Dr. Liebig, 
Dr. Playfair and others have given it at from 40° to 45°. 
The sketch by Lieutenant Wales given in Lieutenant Colebrooke’s paper, save that it 
represents an inclination of about 60° to the sides of the cone, conveys the best idea of the 
island of any of the numerous figures which have been published. It was reproduced by 
Yon Buell, and copied from him by Sir Charles Lyell, Dr. Daubcny, Dr. Buist, &c. Yon 
Buck, in his “ Menfoir on the Canary Islands,” gives the height of the cone at 1,690 Paris feet. 
His account, though apparently derived from Lieutenant Colebrooke’s paper alone, contains 
the statement that the sea penetrates into the circle at the base of the cone. This can only 
have been due to some misapprehension of the meaning of Blair’s words, which were as 
follow: “ Tko base of the cone is the lowest part of the island and very little higher than 
the level of the sea.” 
Sir Charles Lvell, in the earlier editions of the ‘Principles,’ framed his account from Von 
Buch’s. In the changes from English into French, and back again into English, the elevation 
of the cone became increased by 48 feet, standing in the 7th edition of the ‘Principles’ 
(1847) at 1,818 feet. It is also there stated that the circular basin inside is filled with the 
waters of the sea, lu the 9th Edition, 1853 (I have not been able to refer to the 8th), Captain 
Miller’s estimated elevation of 500 feet is adopted instead of the former one ; but the statement 
