240 EEPOKT— 1891. 



such in his log. Off Possession Island a current running 

 southward took the ships to windward (Eoss's Voyage, vol. i., 

 p. 195). Off Coulman Island another drifted them in the 

 same direction at the rate of eighteen miles a day (Boss's 

 Voyage, vol. i., p. 204). A three-quarter-knot northerly cur- 

 rent was felt off the Barrier, and may have issued from 

 beneath some part of it. Such isolated observations are of 

 little value ; but were they multiplied, and were the currents 

 correlated with the winds experienced, the information thus 

 obtained might enable us to detect the existence of the straits 

 even where the channels themselves are masked by ice-bar- 

 riers. 



Einally, it is calculated that the centre of the polar ice-cap 

 must be three miles and may be twelve miles deep, and that, 

 the material of this ice mountain being viscous, its base must 

 spread out under the crushing pressure of the weight of its 

 centre. The extrusive movement thus set up is supposed to 

 thrust the ice-cliffs off the land at the rate of a quarter of a mile 

 per annum. These are some of the geographical questions 

 which await settlement. 



In the geology of this region we have another subject 

 replete with interest. The lofty volcanoes of Victoria Land 

 must present peculiar features. Nowhere else do fire and frost 

 divide the sway so completely. Eoss saw Erebus belching out 

 lava and ashes over the snow and ice wdiich coated its flanks. 

 This circumstance leads us to speculate on the strata that 

 would result from the alternate fall of snow and ashes during 

 long periods and under a low temperature. Volcanoes are 

 built up, as contradistinguished from other mountains, which 

 result from elevation or erosion. They consist of debris piled 

 round a vent. Lava and ashes surround the crater in alternate 

 layers. But in this polar region the snow-fall must be taken 

 into account as well as the ash-deposit and the lava-flow. It 

 may be thought that any volcanic ejecta would speedily melt 

 the snow upon which they fell ; but this does not by any means 

 necessarily follow. Volcanic ash, the most widespread and 

 most abundant material ejected, falls comparatively cold, 

 cakes, and then forms one of the most efi'ective non-conductors 

 known. When such a layer, a few inches thick, is spread over 

 snow, even molten lava may flow over it without melting the 

 snow beneath. This may seem to be incredible, but it has 

 been observed to occur. In 1828 Lyell saw on the flanks of 

 Etna a glacier sealed up under a crust of lava. Now, the 

 Antarctic is the region of thick-ribbed ice. All exposed sur- 

 faces are quickly covered with snow. Snow-falls, ash-falls, 

 and lava-flows must have been heaping themselves up around 

 the craters during unknown ages. What has been the result? 

 Has the viscosity of the ice been modified by the intercalation 



