1860.] Account of a visit to Barren Island. 5 



to enter the island. The vapours rose principally from the northern 

 and southern quarters of the edge where the fissures were largest 

 and longest, running both parallel and across the edge. The rocks 

 where the sulphurous vapours issued from between them, wereco- 

 vered vvith reddish and white crusts, indicating the beginning of decom- 

 position of their substance. From the top the horizon and more or 

 less of the sea were visible in all direetions, with the exception of 

 the quarter between South and West. The inner slope of the cir- 

 cular elevation enclosing the valley, had no spurs, but was like a 

 plain wall, falling off with a steep descent all round towards the 

 centre. It had a uniform brownish colour, appertaining either to the 

 surface of larger masses of the rock itself, or being derived from the 

 dry grass and smaller shrubs covering the slope. There were no 

 trees or brushwood visible to correspond to the richer vegetation on 

 the external circumference. Horizontal parallel lines, traceable 

 throughout the circle and rising somewhat like the borders of reced- 

 ing steps, indicated the thickness and strike of the different sheets 

 of lava and tufa which, superimposed upon one another, formed the 

 substance of the circular elevation. A very good transverse section 

 of it had already attracted my attention, where the leffc side of the 

 transverse valley debouches into the sea. Several strata of tufaceous 

 formation, alternating with older rock like lava, could be seen there 

 rising from the rocky beach. One of the most remarkable amongst 

 these was a stratum of rounded stones, like large pebbles, cemented 

 by tufa, exactly like those of the present beach, but at a considerable 

 elevation (about 20 feet) above the high water mark, showing that 

 the sub-marine base of the Island must have been raised since those 

 pebbles had been washed by the sea. All these strata dipped out- 

 wards from the centre of the island, parallel with the external slope 

 of the encircling wall. It is interesting to observe that this slope 

 continúes under the sea level on three sides of the Island at least, 

 at the same inclination as above water, which averages about 35°. 

 This is shown by the soundings, which exceed 150 fathoms at a 

 distance of a quarter of a mile from the shore. 



Judging from what we saw, as I have here attempted to describe 

 it, I would conclude that the circular valley and its walls constitute 

 the cráter of a huge volcanic cone of sub-marine basis, which had 



