166 THE ANTARCTIC. 



rim of the basin is on the whole more level than the outer 

 circle of the island, except at the western entrance to this 

 crater bay, where a steep cliff of about 787 feet descends 

 perpendicularly into the water. The shores have many 

 indentations, some being again the ruins of smaller 

 craters, though other spent craters lie apparently close to 

 the shore without visible communication with the great 

 basin. Thus Lieutenant Johnson of Wilkes' squadron 

 found a small crater of 1,400 feet in diameter in the 

 background of the bay ; it was separated from the great 

 basin by a rampart 394 feet wide, and rising gradually to 

 a height of eighteen feet, while it fell away steep towards 

 the inside, which was full of water rising to the same level 

 as the surface outside. 



According to Webster, the enclosure of the great 

 basin is irregular in form ; it is not only broader but more 

 elevated on the eastern side, attaining a height of 1,575 

 feet (Webster), or even 1,770 feet (Kendall) in Iceberg 

 Hill. The structure of the island is exclusively volcanic, 

 and exhibits many peculiarities. So far as Foster's 

 investigations indicate, the walls of the collapsed crater 

 consist for the greater part of loose eruptive matter, dark 

 ashes, partly solid, as tufas, sands and slack, also pumice 

 stones, all clearly stratified. Basalt, solid and porous, 

 though only very rarely, also obsidian and perlit. These 

 certainly testify against the basaltic nature of the lavas, 

 since perlit is mentioned as occurring in the basalt. An 

 accurate estimate of these rocks could manifestly be 

 made only after thorough chemical and microscopical 

 investigation. Minerals of non-volcanic origin, either as 

 self-existent or enclosed in other substances, are not 

 mentioned. The whole material of which Deception 

 Island is built up is, moreover, exposed to the great 

 changes and the destruction brought about by wind and 

 weather, and by the activity of the solfataras and the 

 fumaroles of the volcanic ruin. At the time of Foster's 



