V. Ball — Volcanos of the Bay of Bengal. 23 



below the sea. Its top and a portion of the side were, no doubt, 

 blown off by a violent eruption, and the present cone was sub- 

 sequently formed inside. The gap or fissure in the surrounding walls 

 bears about north- west-by- west from the centi*e of the island. It is 

 the only place where an entrance can be obtained to the central 

 valley. 



For a long time Barren Island was considered by Yon Buch and 

 others of his school as a most favourable example of his elevation 

 theory of craters. Since, however, the island is in reality only 

 formed of volcanic materials elevated above the sea without a trace 

 of any pre-existing rocks, it is evident that its peculiar form gives 

 no support to that now exploded hypothesis. 



Hot Spring. — Close to the landing-place, there is a hot spring 

 which has been mentioned in several of the accounts of the island. 

 Dr. Play fair found the temperature to exceed 140°, — the limit of his 

 thermometer. Dr. Liebig's thermometer was only graduated up to 

 104°, but judging from the feel to the hands, he estimated it to be 

 near the boiling-point. The Andaman Committee record it at from 

 158° to 168°. At the time of our visit the highest temperature of 

 the water where it bubbled out of the rocks, close to high-water 

 mark, was 130° F. We therefore failed to boil some eggs in it 

 which we had brought with us for the purpose. The water is 

 perfectly clear and sweet, 1 and there was no trace of sulphurous 

 vapours. Strange to say, where, though mingled with the sea, it 

 was still too hot for the hand to be retained in it with comfort, 

 there were a number of brilliantly-coloured fish swimming about. 



Facing the landing-place is the termination of a flow of lava 

 which extends backwards for about a mile to the base of the cone, 

 round which it laps for perhaps f- of the circumference. The height 

 or thickness of this flow of lava is about 10 feet at first, gradually 

 rising to about 50 feet where it emerges from the base of the cone. 

 The upper surface is deeply cleft and covered over with blocks 

 of black cellular lava which rest upon one another in confused 

 piles. Sometimes they are poised so insecurely one upon another 

 that it is a matter of no little risk to attempt scrambling over them. 

 Towards the base of the flow the rock from its slower cooling 

 is more compact and less cellular. In places it contains white 

 crystals of a mineral resembling leucite. In others it is a true 

 basalt with numerous crystals of olivine. 



As pointed out by Dr. Liebig, the older lava seen in the section of 

 the ridge differs from this ; it consists of a reddish matrix with 

 crystals of felspar (probably sanidine), olivine, and augite. A 

 somewhat similar rock occurs on Narkondam. 



On our way to the central cone from the landing-place, we at first 

 endeavoured to avoid the rough surface of the lava-flow by keeping 

 on the slope of the gap ; but after a short distance the bushes and 

 unevenness of the ground compelled us to strike down on the lava, 

 when we found, to our astonishment, a sort of path which must have 



1 The Andaman Committee do not appear to have realized this fact, as they spent 

 no little time and trouble in excavating a well without finding a trace of water. 



