DESCRIPTION OF THE ISLANDS 359 



In support of this it may be remarked that the upper strata of a tabular berg are 

 evidently very much less dense than those of its base and under-water portions ; for the 

 layers of deposited snow, as a rule evenly laid and relatively broad at the top, narrow 

 successively down to the water-line, where they are often compressed to a small fraction 

 of the width of the upper layers and sometimes contorted by strains. 



The presence of many icebergs in the neighbourhood of the South Orkneys is by no 

 means uncommon. From the earliest times nearly every navigator who has visited the 

 group has reported exceptionally large numbers in its vicinity. Nevertheless the number 

 in January 1933 would seem from all accounts to have been an unusually large one. 



It is almost certain that the majority of the bergs which reach the South Orkneys in 

 such profusion have their origin in extensive ice-barriers in the south and west of the 

 Weddell Sea. Bergs shed from these barriers pass directly into the north and north-east 

 bound Weddell Current and so are eventually carried to the South Orkneys to strand 

 themselves in the shallow water to the south of the group. Between 1927 and 1933 

 enormous tabular bergs, one "as large as South Georgia", were reported in the neigh- 

 bourhood of Clarence Island and in the eastern part of the Scotia Sea. In discussing the 

 origin of these veritable "ice-islands" Wordie and Kemp^ state that it seems necessary 

 "to assume that there has been in recent years an unusual break up of barrier ice in the 

 Weddell Sea", and they conclude that the disruption has taken place in the unknown 

 south-west portion of the Weddell Sea, between the Filchner Barrier and North 

 Graham Land. The presence at the South Orkneys of phenomenal numbers of bergs in 

 January 1933 may well be associated with the same cause. The break up of a fifty-mile 

 berg stranded in the shoal water to the north-east of Joinville Island, or on the South 

 Orkneys-Clarence Island ridge, might easily result in the sudden appearance of enor- 

 mous numbers of relatively small, irregular bergs such as we saw. Another possible 

 source of those that congregate at the South Orkneys would be to the east of Coats 

 Land; the resulting bergs would thus go right round the Weddell Sea. 



The capacity of the South Orkneys themselves to produce icebergs is extremely small. 

 According to Pirie^ the forward motion of the glaciers, of Laurie Island at least, is very 

 slight, with the result that they calve infrequently, and when they do, shed only pieces 

 of trifling size and certainly nothing larger than an "ordinary tramcar". 



GLACIATION 



Laurie Island. In 1903-4 the glaciers of Laurie Island were studied by Pirie who 

 published a careful and detailed description of them some years after the return of the 

 ' Scotia' from the Antarctic. In that work^ he observes that the subsidiary rock ridges 

 which branch off the central backbone into the narrow lateral peninsulas of Laurie 



1 Wordie, J. M., and Kemp, S., 1933, Observations on certain Antarctic Icebergs, Geog. Journ., lxxxi, 

 part 5, pp. 431-4. 



- Pirie, J. H. Harvey, 1913, Glaciology of the South Orkneys, Trans. Roy. Soc. Edin., XLIX, part iv, p. 849. 

 ^ Ibid., pp. 837, 838, 839, text-figs. 1-4, plates i, iii, xi. 



