272 Notices of Memoirs — Antarctic Exploration. 



icebergs, and a few pelagic foraminifera. This deposit appears to 

 form a zone right round the earth in these latitudes. Still further to 

 the north the deposits pass in deep water, either into a Globigerina 

 ooze, or into a red clay with manganese nodules, sharks' teeth, 

 ear-bones of whales, and the other materials characteristic of that 

 deep-sea deposit. Since these views, however, as to the distribution 

 of deep-sea deposits throughout these high southern latitudes, are 

 founded upon relatively few samples, it cannot be doubted that 

 further samples from different depths in the unexplored regions 

 vv^ould yield most interesting information." 



The subject of temperature of the Antarctic Ocean was then 

 discussed. 



" The mean daily temperature of the surface waters of the 

 Antarctic, as recorded by Ross, to the south of latitude 63° S. in 

 the summer months, varies from 27-3° to 33-6°, and the mean of all 

 his observations is 2985°. As already stated, his mean for the air 

 during the same period is somewhat lower, being 28-74:°. In fact, 

 all observations seem to show that the surface water is warmer than 

 the air during the summer months. 



" The ' Challenger ' observations of temperature beneath the 

 surface indicate the presence of a stratum of colder water wedged 

 between warmer water at the surface and warm water at the 

 bottom. This wedge-shaped stratum of cold water extends through 

 about 12° of latitude, the thin end terminating about latitude 53° S., 

 its temperature varying from 28° at the southern thick end to 32 5° 

 at the northern thin end, while the temperature of the overlying 

 water ranges from 29° in the south to 38° in the north, and that of 

 the underlying water from 32° to 35°. This must be regarded as 

 the distribution of temperature only during the summer, for it is 

 improbable that during the winter months there is a warmer 

 sui'face layer. 



" In the greater depths of the Antarctic, as far south as the 

 Antarctic circle, the temperature of the water varies between 32° 

 and 35° F., and is not, therefore, very different from the temperature 

 of the deepest bottom water of the tropical regions of the ocean. 

 The presence of this relatively warm water in the deeper parts 

 of the Antarctic Ocean may be explained by a consideration of 

 general oceanic circulation. The warm tropical waters which 

 are driven southwards along the eastern coasts of South America, 

 Africa, and Australia, into the great all-encircling Southern Ocean, 

 there become cooled as they are driven to the east by the strong 

 westerly winds. These waters, on account of their high salinity, 

 can suffer much dilution with Antarctic water, and still be denser 

 than water from these higher latitudes at the same temperature. 

 Here the density observations and the sea-water gases indicate 

 that the cold water found at the greater depths of the ocean 

 probably leaves the surface and sinks towards the bottom in the 

 Southern Ocean, between the latitudes of 45° and 56° S. These 

 deeper, but not necessarily bottom, layers are then drawn slowly 

 northwards towards the tropics, to supply the deficiencies there 



