\N owni . — -Pef roloffical Nofes on South Victoria Land Rocks. 495 



period i]i such a climate all these glaciers did come down to sea-level, and 

 that those that do so now were formerly of far greater extent. This, 

 1 think, is far too hasty a conclusion, especially when we consider that 

 McMurdo Sound has never previously been visited by man, and very little 

 is known of the entire region from the point of view of its physiographical 

 conditions. Some of the so-called glaciers, like that in McMurdo Sound 

 described in the present paper, the Drygalski ice-sheet, and probably others, 

 require more detailed examination before any really definite and satis- 

 factory opinion can be pronounced. 



Within forty miles of our winter quarters were no less than three active 

 volcanoes, one smoking vigorously, the other two quiescent, and in such 

 a volcanic district it is only fair to ask what would be the probable effect 

 of— (1) volcanic eruption, (2) earthquake. 



First with regard to volcanic eruption. For how long would the trace 

 of such an occurrence be perceptible except by actual and close examina- 

 tion of the ground ? Appareii.tly not more than a few weeks. Lava -flows 

 certainly might be conspicuous for a much longer period ; but their age and 

 finer characters are, not to be detected at distances measured by the mile. 

 Ashes and other volcanic ejecta might cover large areas, and under some 

 conditions, such as seen in the Brown Island rubble-mass, would absorb 

 the sun's heat and quickly effect considerable changes in the subjacent 

 snow and ice. Under other conditions the snow might speedily and effec- 

 tively hide all traces of any eruption as visible from a distance. 



Li the matter of earthquakes, their effect might be far more serious, 

 and at the same time even less conspicuous. It is by no means incon- 

 ceivable that the land in the vicinity of McMurdo Sound has undergone 

 some change of level quite recently from a geological point of view. How 

 could it be recognized on a first visit ? Further, what would be the effect 

 of a " good average " earthquake on the sea ice in such a region ? It 

 would certainly mean considerable rupture, with probably a serious effect 

 on the adjacent shores. From such a sheet at the Great Ice Barrier it is 

 quite reasonable to suppose that a single earthquake of any magnitude 

 would make such a difference to that sheet as would take many years to 

 replace. 



The land visited has been seen for the first time, and we have to take it 

 as it stands. To assume its permanency during, say, the last thousand 

 years seems to me to be putting a great deal into a first visit. Had we bee)] 

 able to stay four or five years, or to make an exhaustive survey of the Sound 

 and its shores, we might have been in a different position. Before we talk 

 so emphatically about the recession of glaciation on such limited experi- 

 ence it would be well to bear in mind the possibilities of volcanic energy. 



