io4 



DISCOVERY REPORTS 



In 1933-4 a large number of stations were made near the pack-ice in the South Pacific, 

 and also on a routine section in 8o° W. In the course of a cruise from 1 to 18 January 

 from 74° to 160 W at an average latitude of 67 23' S, the silicate content of 

 Antarctic bottom water at sixteen stations averaged 6475 mg. at a depth of 4000 m. 

 On the return journey at a slightly higher average latitude of 68° 56' S from 171^ J to 

 8o° W the average content at a depth of 4000 m. at fifteen stations was about 

 6600 mg. In November of the same year ten stations at an average latitude of 64 S 

 between 8o° and no°W averaged a silicate content of 6100 mg. at 4500 m. The 

 above data are not sufficient to show the seasonal variation but give the approximate 

 amount of the silicate content. Future investigation is likely to show a periodic 

 variation in the nutrient salt content of the bottom water in this region as is indicated 



LATITUDE 68°S 

 1 o 



6,6' 





la un to 



torn 

 cm- 





O DECEMBER 1933 



X MARCH 



• SEPTEMBER 



A OCTOBER 



■ NOVEMBER 



Fig. 29. Graph showing the variation of the silicate content from south to north at the deepest observation 



(3500 m. or deeper) in 8o c W. 



by Fig. 29. From this figure, which gives the silicate content at the deepest observa- 

 tions in 8o° W northwards from the ice-edge, it seems that at the south end of the 

 sections the silicate content of the bottom water was greatest in December and lowest 

 in September and October, the difference being very considerable. At the latitude of the 

 Antarctic convergence no great seasonal change is shown, but at the northern end of the 

 sections some variation occurred, the December results again being greatest and those 

 of October least. 



As a summary of the present data on the silicate content in the Antarctic bottom 

 water it may be said that silicate is found in large quantity in this current particularly in 

 the Antarctic zone where as much as 8600 mg. has been recorded ; a more usual content 

 is, however, 6000-7000 mg. 



On account of the northerly component in the movement of this current large quantities 



