52 DISCOVERY REPORTS 



subjected to enormous pressure for great floes had been rafted up and were piled high in in- 

 describable confusion. We realized then the nature of the forces which had overwhelmed the 

 Endurance' . 



In Fig. I I have plotted the majority of the stations where various types of plankton net suit- 

 able for the capture of the krill or its larvae were fished and subsequently examined.^ Unavoidably a 

 number of stations have had to be omitted, notably in localities such as the South Georgia whaling 

 grounds and the Bransfield Strait where there has been particularly heavy crowding. In the former 

 locality alone 385 closely spaced observations should appear. These together with the equally closely 

 spaced observations in the Bransfield Strait are shown in Figs. 2 and 3, only a selection of them 

 being reproduced on the circumpolar scale. For the rest it is apparent that apart from the gaps already 

 mentioned the Antarctic Ocean proper, taking that as meaning everywhere southward of the Antarctic 

 convergence, has been substantially covered, while the warmer Subantarctic and Subtropical waters 

 to the north, although on the whole less intensively fished, have not by any means been neglected.^ 



Throughout the summer and autumn months, that is to say from December to May, but particularly 

 in January, February and March, much of the Antarctic Ocean, as Mackintosh and Herdman (1940) 

 show, is relatively ice-free, or at any rate covered by navigable pack, and at one time or another during 

 these months our vessels have reached high latitudes, on more than one occasion carrying their 

 observations up to the shores of Antarctica itself. From June to November on the other hand, that 

 is to say throughout the winter and spring months, the pack extends as an impenetrable barrier far to 

 the north of the continental land^ with the result that our observations then are restricted in most 

 sectors to relatively low latitudes. The striking disparity between the southern limits of the two sets 

 of observations is shown in Fig. i in which open circles are employed to indicate the summer-autumn 

 ones and solid black circles the winter-spring ones. Only in the Falkland sector between 30° and 

 60° W do the southern limits of the black and open circles coincide. The chief reason for this is 

 that it is here (Herdman, 19486) that we find the main out-thrusting of pack-ice from the Weddell 

 Sea. There is always a great deal of heavy ice about, presenting even in summer an effective barrier 

 to southing vessels. Broadly, around the greater part of Antarctica, the average distance separating 

 the southerly limits of the summer-autumn and winter-spring observations is from 300 to 400 miles. 

 The gap is most conspicuous, however, in the Atlantic-Indian Ocean sector between 30° W and 

 60° E where the summer-autumn observations extend for as much as 600-800 miles farther south 

 than the winter-spring ones ; and this again springs from the northerly encroachment of the ice-sheet 

 that in winter covers so much of the Weddell stream. 



Thus it transpires, although our observations are spread over every month of the year, a vast area 



1 This chart includes 84 stations made by the Norwegian (' Norvegia ' and ' Vikingen ' ) expeditions that visited the Antarctic 

 between 1927 and 1931 and 63 stations made by the British-Australasian (B.A.N.Z.A.R.E.) expedition in 1929-31 (Johnston, 

 1937). It includes too the post-war observations of R.R.S. 'Discovery 11' in 1950-1 (Herdman, 1952). 



^ In a brief reference to the development of world oceanography over the last 30-35 years Zenkevich (1958) unaccountably 

 overlooks this massive coverage of the southern seas (already shown in many published papers), stating that in common with 

 other parts of the southern hemisphere ' systematically acquired data on the distribution of plankton ' from Antarctic waters 

 were very limited. 



^ Continental at least in the sense that the vast ice-sheet that covers it is continental. Doubts have been expressed as to 

 whether the whole of the underlying rock is continental, it having been suggested it may comprise the separate parts of 

 an archipelago. Recent seismic and gravimetric measurements by Russian I.G.Y. expeditions, however (Shumskiy, 1959), 

 show that East Antarctica at least is ' a typical continent submerged by the weight of a thick ice sheet to a depth of several 

 hundred metres, and in some parts to below sea level. Only in West Antarctica is there the probability that a chain of 

 mountainous islands is joined to the East-Antarctic Continent by the over-lying ice sheet'. See also Anon. (1960a) and 

 Robin (i960). A channel does it seems cut through the supposed continent from the Ross to the Bellingshausen Sea 

 (Bentley and Ostenso, 1961). 



