3i6 DISCOVERY REPORTS 



the West Wind drift is very variable. It is greatest in the Drake Passage, where it is compressed 

 between Cape Horn and Graham Land, and diminishes towards the east, but even in the Drake 

 Passage {Antarctic Pilot, 1948, p. 55) the majority of the currents experienced by shipping are of the 

 order of i knot or less.^ In April 1842 Ross (1847) found the current there setting to the east 

 at a rate of from 12 to 16 miles a day. South of Australia, although speeds of up to 15 and 18 miles 

 a day have been recorded, the average rate of the easterly movement seems to be of the order of from 

 6 to 10 miles a day (Mawson, 19400). 



Another typical example of northerly extension of East Wind influence, as will be shown more 

 emphatically later (p. 325, Fig. 86), is provided in Fig. 75 by the very small black West Wind plot 

 south-east of Kerguelen. 



Table 61. Vertical distribution of the larvae at Station 64'] 



Second 

 Calyptopis 



6 



In the West Wind region of the Scotia Sea, that is, in that part of it between the northern boundary 

 of the Weddell drift and the Antarctic convergence, there is one major concentration and three minor 

 concentrations of surface Calyptopis forms, all four occurrences in March. The major occurrence 

 is represented in Fig. 75 by the black and white plot of the second highest order of magnitude 

 immediately to the east of meridian 60° W. It occurred at Station 647, where as already noted (p. 306), 

 the bottom water, spreading from a secondary locus of its formation between the South Orkney and 

 South Shetland Islands, seems to have been carrying large numbers of eggs and deep larvae, some of 

 which, the vast majority as Metanauplii, had already risen to the 1000-500 m. level. The vertical 

 distribution of the total larval population encountered here is shown in Table 61 from which it is 

 clear that the surface population, being 99% First Calyptopes, represents the fairly recent product of 

 the moulting of the Metanauplii rising from below. The three minor concentrations encountered a 

 little farther east, represented in Fig. 75 by the black and white plots of the second lowest order 

 of magnitude, had no deep larvae below them and all, therefore, may have come from the west, having 

 sprung perhaps from West Wind risings such as that for instance recorded at Station 647. 



There is little further to add concerning the March and April distribution of the surface Calyp- 

 topes, except perhaps to note again their pronounced abundance in the East Wind- Weddell surface 

 stream and their local abundance in such strictly limited areas of the West Wind drift as are affected 

 by cold surface emanation from the East Wind zone. 



May-June. The distribution of the surface Calyptopes for May-June, after which they outgrow 

 themselves and are no longer to be found in the plankton,^ is shown in Fig. 79. The Antarctic 

 winter has now begun and the sea become frozen over far to the north of the continental land. The 



1 Smith (1920), however, states that through this narrow passage the current often flows at a rate of as much as 50 miles 

 a day, but this probably only occurs when the westerly winds are exceptionally strong. The average speed of the drifting 

 derelict ' Dumbartonshire', abandoned by her crew in August 1894 in 40° S, 40° W, works out over a distance of 1850 miles 

 at around 12 miles a day (Russell, 1895). For 9 days, however, she appears to have drifted at 43 miles a day, probably as 

 Russell suggests owing to a gale of wind. 



2 In the plankton at least of the northern or Weddell zone. The Calyptopes may not yet in fact have outgrown themselves 

 (p. 285, note 4) in the plankton of the now largely inaccessible East Wind zone. 



