86 
Records of the Geological Survey of India. 
[vol. VI. 
From the preceding we may gather the following. The volcano has probably not been 
in violent eruption since the years which closed the last and commenced the present century. 
The lava-flow which stretches from the entrance open to the sea to the base of the cone 
was probably poured out during this period, and raised the level of the encircling valley 
some 40' above its elevation in 1789, when Blair saw it. He makes no mention of a lava 
stream in his time. If it did not exist then it cannot—as has been supposed by some—have 
been instrumental in the formation of the entrance. That this fissure was probably due to 
other causes we shall presently see. 
From Lieutenant Wales’ figure it is apparent that no material change has taken place in 
the general configuration, and as it has been shown that 1,800 feet cannot have been the true 
height, and about 020 probably was, no great alteration in the level is likely to have 
taken place. 
General appearance of the Island .—Seen from, any side but the north-west, Barren 
Island appears as a nearly flat-topped hill with numerous spurs running down into the sea. 
From some aspects, however, the top of a central cone with a column of smoke rising from it 
is discernible. 
As the north-west side opens up to view, it is first realised that the island consists of 
a circular ridge forming a huge amphitheatre, which is broken down at one side for a dis¬ 
tance of perhaps 150 yards to the level of the sea. The view obtainable through this entrance 
discloses a bare cone which rises from the centre of the valley. Except at a sort of shoulder 
not far from the top, and at two peaks close to the summit, no rocks are seen on this cone, 
its smooth sides being covered with grey ash and occasional strings of shingle. Towards the 
top some whitish patches are seen, due to the presence of gypsum mixed with the ash. 
The total diameter of the island is, on the authority of Lieutenant Heath cote, 2,970 yards. 
The circuit of the island, from the time it took us to row round, I estimated at about six miles. 
The high encircling ridge is formed of somewhat irregularly deposited layers of lava, ash 
and conglomerate, which dip away from the centre. A section of these may he seen on the 
left hand of the gap or entrance, and others at various points on the sea-face, no two of 
them corresponding exactly in character. 
These beds or layers generally dip at angles of 35°—40°, which inclination appears 
to he continued steadily under the sea, as bottom, except at one place, has not been found 
with a line of 150 fathoms at £ of a mile from the shore. This steepness has been un¬ 
favourable to the formation of a fringing reef of coral of any magnitude, such as we find 
surrounding some of the Andaman and Nicobar groups. 
The elevation of this outer ridge varies somewhat in places, but it probably nowhere 
is much in excess of 1,000 feet. Its highest points are towards the south and west. 
The appearance presented by the inner scarped face of this amphitheatre is very 
peculiar. In several places cornice lines mark the position of particular beds, but a 
purplish grey, or in places brownish, ash spreads over the steep slopes, except towards the 
south-west and ivest, where there are some trees and shrubby vegetation. To the north, south 
and east a few tufts of grass—generally arranged in long vertical lines, the first being a sort 
of protection to those hulow it—are the only plants which have managed to establish a footing 
in the loose ash. 
The outer slopes facing the sea are for the most part covered with a luxuriant vegetation, 
in which large forest trees may be discerned. These latter attract considerable numbers of 
fruit-eating pigeons (Carpophaga bicolor). 
From its composition and character, it is evident that this ring of cliffs is the remnant 
of the original cone which gradually rises from below the sea. Its top and a portion of the 
