SOUTH SANDWICH ISLANDS. 149 



to be assumed, and it is possible that this activity has not, 

 as yet, entirely ceased. This conclusion may be drawn 

 from an interesting observation made by Weddell. He 

 had ascended a hill in Adventure Bay for the purpose of 

 taking altitudes of the sun ; but, after setting his quicksilver 

 horizon, he noticed that although the atmosphere was per- 

 fectly still, and he himself was not conscious of any vibra- 

 tion, the surface of the quicksilver trembled constantly in a 

 lively manner, a phenomenon that can only be accounted 

 for on the supposition that some seismic disturbance im- 

 perceptible to Weddell himself was taking place. Whether 

 beside these indications of the structure of the rocks 

 volcanoes also exist on South Georgia must remain 

 doubtful. Klutschak certainly marks some, but these 

 are so vague and uncertain that much caution is required 

 before coming to any conclusion respecting actual volcanic 

 activity. 



3. THE SOUTH SANDWICH ISLANDS. 



The small group of Clerk's Rocks lying south-east of 

 South Georgia in latitude 54° 55' S. and longitude 34° 

 46' W., guide us across to the South Sandwich Isles. 

 This rocky group, consisting, according to Cook, of three 

 or four rocks, seems to be a remnant of a larger island 

 gradually abraded and engulfed by the ceaseless activity 

 of the surf; indeed this inference is suggested by the 

 existence of a submarine plateau at a depth of only 330 

 feet spreading beyond the rocks a distance of nearly five 

 miles, while the depth between these and South Georgia 

 according to Cook's soundings, must exceed 1,000 feet. 



As the map indicates, the South Sandwich Isles form 

 a curve opening- to the west, of which the most northerly, 

 Sowadowskji Island, is situated in latitude 56° 18' S. and 

 longitude 27° 29/ W., while the position of the most 

 southerly, Southern Thule, latitude 59° 26' S. and longitude 



