PREFACE 



A DISTINGUISHED Norwegian geologist has remarked : * " While we know fairly well 

 the effect of running water from glaciated lands with a wet climate, we practically do 

 not know anything of the way in which a continuous ice covering pure and simple 

 may sculpture a land." Herein lies one of the many charms of that great white con- 

 tinent — so vast that even where narrowest it would stretch from Calais to the Caspian 

 — viz. that its ice covering, except for the Antarctic Horst in the Eoss Sea region, is 

 nearly continuous. One might, therefore, imagine that in Antarctica Reusch's ideal is at 

 present realised ; and so it is, but to a comparatively limited extent. Man has arrived 

 in Antarctica too late, just as civilised man has been in Europe too late, has gone to 

 North America too late, and still goes to Greenland and Sjiitzbergen too late, to 

 observe anything like the full effect of a continuous ice covering in sculpturing land. 

 Probably everywhere to-day the ice-fields of the world are on the wane, in spite of 

 what appear to be exceptions in the case of local advancing glaciers. De Geer has 

 suggested that ice does not necessarily flow evenly and steadily, as water does, but is 

 subject probably to intermittent outrushes followed by short epochs of retreat. 

 These outrushes may be due to prolonged accumulation of inland ice setting up a 

 critical pressure ultimately sufficient to overcome frictional resistance and resistance 

 to shearing. The ice then moves away rapidly towards lower levels, and in polar 

 regions thrusts itself into the sea, and across the sea-floor, until its seaward edo-e 

 floats and breaks away as bergs. Such an epoch of activity may be followed by a 

 resting stage, when ablation of ice, partly through the breaking away of bergs, partly 

 through thaw and evaporation, exceeds what is added through ice flow and snow 

 precipitation. Thus in one and the same district one glacier may be rapidly advancing 

 while an adjacent glacier is retreating, as is the case in Spitzbergen with the Sefstrom 

 Glacier and the Von Post Glacier respectively.! With the exception of such glaciers 

 as are in a stage of temporary advance all the ice masses in the world are probably 

 dwindling. Certainly the Antarctic ice sheet is decreasing rapidly, and this ice 

 shrinkage has been general, as fur as we know, over the whole area of the Antarctic 

 Continent, from circle to pole. We can no more judge of the work that the 

 Antarctic ice has accomplished by what it is accomplishing now in sculpturing the 

 local land than we can measure the erosive action of a river when in flood by what 



* Congr^s Geologique International, XI. Session, Stockholm, 1910. " A Few Words on the Effects of 

 Glacial Erosion in Norway,' H. Reusch. 



•f We are indebted to G. W. Laraplugh, F.R.S.,for kindly calling our attention to this featuie. 



ix Jj 



