THE ICE. 265 



would even appear that in 1892 the drift of the gigantic 

 iceberg brought in its train sea ice as far north as 41 or 

 42 S. ; however, this may have been mere fragments of 

 icebergs, since it can hardly be supposed that in the sea 

 surface, greatly chilled though it was by the melting 

 glacier ice, the salt-water ice could have drifted so far 

 north, seeing that it thaws so much more readily. 



Both kinds of ice, icebergs, and sea ice bring to the 

 temperate latitudes of the southern ocean large quantities 

 of cold water ; nevertheless these do not suffice to replace 

 the water withdrawn from the tropics by evaporation. The 

 necessary compensation is effected by the exceedingly slow 

 movement of the icy cold waters at the bottom of the 

 sea coming from the south polar regions. This forward 

 movement extends to the Equator and far to the north 

 of it. On the other hand, the melting Antarctic ice causes 

 a great reduction of the surface temperature of the sea 

 in higher latitudes, and also of the lower strata of water 

 in the middle latitudes, in fact, over the whole extent 

 of the drift of the icebergs. The investigations of the 

 Challenger have shown that in the neighbourhood of the 

 real pack-ice the surface temperature is uniformly below 

 3 2 F., but above 2 8 c F., the freezing-point of sea water. 

 Farther north the temperatures gradually increase, but 

 between the higher temperatures on the surface, and a 

 stratum of equal temperature at a depth of from 500 to 

 600 feet a body of colder water is wedged in, extending 

 to about 53° S. This is due to the fact that the glacier 

 ice melting in salt water forms with the later a sort of 

 freezing mixture, which reduces the temperature of these 

 mixed waters from 32 F. to 28*9° F. But this mixture 

 cannot sink to the bottom, being partly fresh water, and 

 therefore specifically lighter than the lower stratum which 

 though warmer is more saline. For organic life in the sea 

 this fact is of great importance, as the richest animal life 

 is most abundantly developed in this cold and cool water. 



