ANTARCTIC INTERMEDIATE WATER 75 



where the surface water belongs to the Agulhas current system, and at about 600 m. 

 outside the influence of this system. The difference in depth of the intermediate current 

 is due to the large volume of tropical and subtropical water borne by the Agulhas 

 current. The silicate distribution in this area is shown in Plate VIII, where it is seen 

 that at Sts. 1554 and 1555 in section 4 the content at 1500 m. is of the order of 2400- 

 2700 mg. against 1050-1900 mg. at 600 m. at Sts. 1556 and 1557 to the south of the 

 Agulhas water. In April 1932 a section was made between Cape Town and the ice-edge 

 north of Enderby Land. This section (5, Sts. 845-855) is shown in Plate IX, from 

 which, cf. Deacon, 1937, Plate XIV, it is seen that the silicate content at the depth of 

 minimum salinity was greatest towards the north, being of the order of 2200 mg. in 

 the north and of 1600 mg. at 48 14-6' S in the south. 



Between the Crozets and Durban in May 1934 the silicate content at the depth of 

 minimum salinity increased from 800 mg. at about 350 m. at St. 1369 in 42 25-8' S, 

 just south of the subtropical convergence, to a value of 2750 mg. at a depth of 1500 m. 

 at St. 1372 in 34 01 -8' S. A year later the silicate content a short distance to the west 

 of the previous section was 1800 mg. at the salinity minimum of the intermediate current 

 in the south, a value which increased to 2750 mg. in the north. 



Plate XI shows the vertical distribution of silicate content along section 6 between 

 the ice-edge in 64 38' S, 44 16' E and Guardafui in 1 1° 32' N ; the section is composed 

 of two sets of observations from different years. The silicate content at the salinity mini- 

 mum of the layer increased northwards from a value of 800 mg. at 42 25-8' S as the 

 depth of the current became greater, until a value of 2400 mg. was reached at 1500 m. 

 at St. 1570 in 28 42' S. North of this latitude the depth of the current lessened and 

 the nucleus was usually found between 600 and 800 m., the silicate content ranging 

 from 1500 mg. to 2200 mg. in a series of crests and troughs. 



The vertical distribution of silicate in section 8 south of Australia in May 193 2 between 

 Cape Leeuwin and the pack-ice in 130 07' E is shown in Plate XIII. The intermediate 

 current had a content of 1900 mg. at the depth of minimum salinity near Australia, the 

 content falling southwards as far as 43 53-1' S where it was 1400 mg., rising again 

 to 1900 mg. at St. 881 in 47 S. 



There are no observations of silicate content south of the Tasman Sea. 



South-east of New Zealand two sets of observations are available along sections 12 

 and 13, one, Sts. 942-948, in September 1932 and the other, Sts. 1277-1281, in January 

 1934. The vertical sections are given in Plates XVIII and XX respectively. In the 

 September section from Wellington to the pack-ice north of the Ross Sea the depth of 

 the minimum salinity of the intermediate current varied between 800 and 300 m., being 

 deepest at St. 947 in the deep basin about half-way between the Antarctic and sub- 

 tropical convergences. Near New Zealand the content at the nucleus of the current 

 was 700 mg., a value which fell towards the south as far as 49 24-6' S where it was only 

 450 mg., and south of this position it increased to a value of the order of 1 500-1700 mg. 

 In the January section from the pack-ice north of the Ross Sea to Auckland the depth of 

 the salinity minimum increased from 300 m. at 53 58' S to 900 m. at 47 16-5' S and to 



