CLIMATE. 237 



If at the comparatively low latitude of 54 S., in a 

 climate that is purely oceanic, albeit greatly modified by 

 the ice covering of the island, such low winter tempera- 

 tures are recorded, it is obvious that much lower readings 

 of the thermometer must prevail in the winters of the 

 Antarctic regions proper, i.e., south of the Antarctic circle. 

 In the winter half-year, when no heat comes in at all, 

 radiation from this country, wholly covered as it is with 

 ice and snow, must produce an intense cold of the air 

 resting over the country, and in connection therewith a 

 barometric maximum at least as high as that of eastern 

 Siberia. The winds originating there must contribute 

 their share to the formation both of the more or less 

 complete ice coating covering the bays that penetrate 

 deeply into the land, and of the narrow belt of sea ice 

 along the northern coast. Although the very powerful 

 breakers of the southern ocean may, in numerous places, 

 reduce the ice covering to fragments, yet even such a 

 partially-closed ice covering will prevent the sea from 

 effectually warming the air resting over the land. Thus 

 it happens that the ice mantle has the same climatic 

 effect as land has, and contributes to the increase in space 

 of the thermometric minimum and barometric maximum. 



The causes of the extraordinary low summer tempera- 

 tures even of the sea are naturally, like all the climatic 

 phenomena of the south polar regions, still hidden from 

 us ; judging by the scanty observations so far made, 

 three causes might be suggested. Firstly, the complete 

 glaciation of Antarctic lands, which must reduce by air 

 currents the temperature of the surface of the sea and of 

 the atmosphere resting over it ; secondly, the enormous 

 ice masses formed in the sea itself, in the shape of sheets, 

 blocks, or most numerous and gigantic icebergs ; thirdly, 

 the heavy clouds hovering over the Antarctic waters 

 which often, if not always, absorb the heat of the sun just 

 in summer. During all his three voyages Ross has within 



