18411882] ICE-ACTION 167 



boulders, which I attributed to the violent impact of icebergs Letter 513 

 or coast-ice. I can offer no opinion on whether the more 

 recent changes of level in England were or were not accom- 

 panied by earthquakes. It does not seem to me a correct 

 expression (which you use probably from haste in your note) 

 to speak of elevations or depressions as caused by earth- 

 quakes : I suppose that every one admits that an earthquake 

 is merely the vibration from the fractured crust when it 

 yields to an upward or downward force. I must confess that 

 of late years I have often begun to suspect (especially when 

 I think of the step-like plains of Patagonia, the heights of 

 which were measured by me) that many of the changes of 

 level in the land are due to changes of level in the sea. 1 I 

 suppose that there can be no doubt that when there was 

 much ice piled up in the Arctic regions the sea would be 

 attracted to them, and the land on the temperate regions 

 would thus appear to have risen. There would also be some 

 lowering of the sea by evaporation and the fixing of the 

 water as ice near the Pole. 



I shall read your paper with much interest when 

 published. 



To J. Geikie. Letter 514 



Down, Dec. I3th, 1880. 



You must allow me the pleasure of thanking you for the 

 great interest with which I have read your Prehistoric Europe? 

 Nothing has struck me more than the accumulated evidence of 

 interglacial periods, and assuredly the establishment of such 

 periods is of paramount importance for understanding all the 



their occurrence at a height of 1300 feet by assuming that the gravel 

 and sand had been thrust uphill by an advancing ice-sheet. (See 

 H. B. Woodward, Geology of England and Wales, Ed. IL, 1887, 

 pp. 491, 492.) Darwin attributed the shattering and contorting of the 

 slates below the drift to " icebergs grating over the surface." 



1 This view is an agreement with the theory recently put forward by 

 Suess in his Antlitz der Erde (Prag and Leipzig, 1885). Suess believes 

 that " the local invasions and transgressions of the continental areas by 

 the sea " are due to " secular movements of the hydrosphere itself." 

 (See J. Geikie, F.R.S., Presidential Address before Section E at the 

 Edinburgh Meeting of the British Association, Annual Report^ 

 p. 794.) 



2 Prehistoric Europe : a Geological Sketch, London, 1881. 



