146 DISCOVERY REPORTS 



Pack-ice. During the winter, so far as is known, the South Sandwich Islands are com- 

 pletely surrounded by pack-ice from the Weddell Sea. The summer conditions vary 

 greatly : in normal years the more northerly islands are probably free from ice for several 

 months, but sometimes they are all unapproachable; and occasionally, in a season of 

 unusual mildness, open water may surround the entire group. 



The direction from which the pack-ice reaches the islands is not clear from the 

 existing records. The set being north-easterly it would be expected that the western 

 side would be the first to be closed in, and this is what Capt. Hansen found when he 

 visited the group in 1927. Both Cook and Bellingshausen, however, found the western 

 side open, and the latter at least, as his chart shows, met with heavy ice to the eastward. 

 On the whole it seems almost certain that the pack generally arrives from the south-west, 

 but that its local distribution about the islands may vary greatly in accordance with the 

 prevailing winds. 



Icebergs. Icebergs, both tabular and weather-worn, were plentiful at all the islands, 

 and many of them were stranded near the shores. They were most numerous at Visokoi 

 and to the north of the rocky islets lying to the west of Bristol, where nineteen were 

 visible at one time. The number of black bergs, carrying mud and stones from the 

 moraines of the glaciers where they were formed, was unusually large during the season 

 1929-30. Three of the nineteen referred to above were of this type, and later, in the seas 

 to the west of the islands, many more were observed. These bergs are invariably parti- 

 coloured, one portion being black and the other white, and it is noteworthy that almost 

 without exception there is a sharp and perfectly straight line of demarcation between 

 the black and the white: the black portion is always completely black and quite opaque. 

 There is in addition another type of berg, of which a good example was seen at Visokoi. 

 This is in most respects closely similar to the morainic type, and at a distance may easily 

 be mistaken for it ; but on near view it is found that the black is replaced by a very dark 

 but translucent bottle-green colour. This dark green part, like the black of the morainic 

 bergs, is always smoothly rounded by water action, pointing to the probability that it 

 was originally on the underside. We have, however, seen to the north-east of the South 

 Orkneys a stratified and tri-coloured berg, in which the lower part was black and the 

 upper dark green, with a narrower middle layer of pure white. We are unable to suggest 

 how these dark green bergs are formed, and have not found any reference to them in 

 the literature at our disposal. Priestley, in his valuable account of Antarctic icebergs, ^ 

 mentions neither the morainic nor the dark green types, and from this, as well as from 

 Dr E. H. Marshall's personal experience in the whaling factory 'C. A. Larsen' in 

 1928-9, it appears that such bergs are either absent from the Ross Sea or are extremely 

 scarce. 



No very large tabular bergs were seen round the South Sandwich Islands, but one 

 with an estimated length of over 60 miles was met on our passage from South Georgia : 

 we rode out a full gale of wind in comfort under the lee that it afforded. Bergs with 

 narrow bands of hard blue ice were seen on one or two occasions. 



1 Priestley, "Glaciology", British Antarcl. (' Terra Nova') Exped. 1910-13, pp. 402-17 (1922). 



