DESCRIPTION OF THE ISLANDS 363 



the peaks at the south-western corner of Coronation Island "great irregular masses of 

 ice of a porous structure stood out to windward" while the rapid deposition of rime at 

 sea-level out of thick fog was observed by Mossman^ at Scotia Bay during the winter of 

 1904. 



From the influence of these warm damp winds Signy Island is largely protected by 

 the higher mass of Coronation Island, and it is to this more than anything else that its 

 comparatively ice-free condition is probably due. No doubt there are other factors 

 involved, such as the general low level of the island, but that at any rate cannot be 

 the deciding factor in view of the marked glaciation at equally low levels of more 

 northerly parts of the group. 



Powell Island. Powell Island is narrow, high and steep. It is covered largely by 

 highland ice, which is light in the extreme south (Plate XXII, fig. 2) but considerably 

 heavier at the northern end of the island where it gives rise to suspended cliff glaciers 

 (Plate XXII, fig. 3). 



Other Islands. With the exception of Christoffersen, Saddle and Larsen Islands, 

 which are all fairly high, none of the smaller islands or islets is at all glaciated. 

 Christofi^ersen and Larsen have some highland ice and Saddle Island has a small cliff 

 glacier on the southern face of its larger peak (Plate XXV, figs, i, 3). On Fredriksen 

 Island there are a few patches of permanent snow (Plate XXIII, fig. i) and steep rocky 

 islets such as the Inaccessibles have light snow-caps (Plate XXIV, fig. i). 



PHYSIOGRAPHY, WITH A NOTE ON ROCK JOINTS 



Pirie^ remarks that "the South Orkneys present the features of a dissected upland, 

 whose main outlines probably owe their origin to glacial action when the land stood at a 

 higher level, although the present-day rock features are largely the result of sub-aerial 

 weathering, and the rock-shattering action of frost". The main features of the topo- 

 graphy, however, have not been produced by the action of the existing glaciers but by 

 that of a heavier and more extensive glaciation in the past. The detached or partially 

 detached ice formations which exist on the South Orkneys to-day are thin and press 

 lightly on the land except along the coast, and from Pirie's observations^ they would 

 appear to be largely at a standstill or possessed of an extremely slow forward motion. 

 In a few there is evidence of slight retrogression within recent times. Of the former 

 heavier and more extensive glaciation evidence is not wanting. According to Pirie'* 

 "the whole outline of Laurie Island is suggestive of ice action and sculpturing on a scale 

 much greater than that which the present-day glaciers could accomplish", while the 

 existence of numerous roches moutonnees and islands of rounded outline all round the 

 coast is evidence that the glaciers once extended far beyond their present limits. 

 Incidentally, in these glacier-rounded islands he finds strong evidence of a former ex- 

 tensive depression of the land mass, for he states that the glaciation of an island like 



1 The Voyage of the 'Scotia', p. 330. 



^ Pirie, J. H. Harvey, 1913, loc. cit., pp. 837 and 853. 



3 Ibid., pp. 849 and 853. ■• Ibid., p. 853. 



