8 Account of a visit to Barren Island. [No. 1, 



south-western slope by its angle of descent being mueb smaller thau 

 that of the north-eastern slope. 



The sulpbur on the top of the cone occurs in such quantity in the 

 cracks and fissures, often lining them to the thickness of more than 

 half an inch, that the question naturally arises, whether the sulphur 

 could not be worked with advantage. 



Although in the immediate neighbourhood of the cráter, where 

 the fissures are numerous, the ground seems to be completely pene- 

 trated with sulphur, this is not so evident in other parts, only a fevv 

 feet lower, where the surface is unbroken. There are however some 

 reasons which seem to promise that a search might be successful. 

 In eruptive cones, like that of Barren Island, there is always a cen- 

 tral tube, or passage, connecting the vent in the cráter with the 

 heat of volcanic action in the interior. In this tube the sulphur, 

 generally in cornbination with hydrogen, rises in company with the 

 watery vapour, and is partly deposited in the fissures and interstices 

 of the earth near the vent, the remainder escaping through the 

 apertures. 



If in the present case we admit the sensible heat of the ground of 

 the upper third of the cone to be principally due to the condensation 

 of steam, a process of which we have abundant evidence in the stream 

 of hot water rushing out from underneath the cold lava, it is not 

 improbable that the whole of the upper part of the interior of the 

 cone is intersected with spaces and fissures filled with steam and sul- 

 phurous vapour, these being suíhciently near the surface to permit 

 the heat to penétrate. It is therefore not unlikely that at a modér- 

 ate depth we should find sulphur saturating the volcanic sand that 

 covers the outside of the cone. 



I only speak of the outside, as we may conclude frorn the evidence 

 we have in the rocks of lava in the cráter and those bulging out on 

 the side, that the structure of the cone is supported by solid rock near- 

 ly to its summit, the ashes covering it only superficially. 



From vvhat has been said above, the probability of sulphur being 

 found near the surface disposed in such a way as to allow of its being 

 profitably exhausted, will depend on the following conditions : 



First. — That the communication of the central canal, through 

 which the vapours rise, with its outlets, be effected not through a few 



