284 Correspondence — G. W. Lamplugh. 



Another depression to 40 or 50 feet filled up these ravines. Then 

 came final re-elevation, and it is possible that a downward movement 

 is now in progress. 



COIiDBESIPOliTIDElsrOiE. 



NAMES FOE BRITISH ICE - SHEETS. 



Sir, — Although Professor Bonney does not, I believe, at present 

 allow himself to be included among " glacialists who hold the 

 'land-ice theory,'" to whom my letter on the above subject (Geol. 

 Mag., March, 1901, p. 142) was addressed, his comments (Geol. 

 Mag., April, 1901, p. 187) are particularly welcome as he shows, 

 by practical application of two of the terms, that the proposed 

 nomenclature may have its advantages even to the opponents of the 

 ' land-ice theory.' Granting that the former existence of ice-sheets 

 in this country is a disputed inference, we may nevertheless find 

 the suggested terminology convenient in the discussion, even when it 

 is denied that the terms represent anything more than an ill-founded 

 conviction. From Professor Bonney and those who think with him 

 I ask no more than that the nomenclature of the British Ice-sheets 

 be accepted on this basis. 



By the way, I will seek Professor Bonney's permission to amend 

 his simile ; surely, in this case it is not that the glacialist is counting 

 his birds before they are hatched, but after they are flown, by the 

 indications in the roost. 



In his playful suggestion of ' Dogger-fjeld ' as a name for the 

 ' East British Ice,' and in his accompanying argument as to 

 the direction of ice-flow. Professor Bonney seems to have taken 

 for granted that the Dogger Bank was a pre-glacial feature. But 

 there is much reason to believe that this Bank is of glacial origin, 

 while of the pre-glacial contours of the floor of the North Sea we 

 know nothing. In areas of low relief the radial point of ice-flow 

 must depend principally upon the incidence of maximum snowfall, 

 and under changing conditions of climate may not remain fixed 

 in the same place. I have elsewhere set forth facts indicating that 

 the East British Ice underwent great changes in this respect during 

 the progress of the Glacial Period. 



The issue raised by Professor Bonney as to the transport of the 

 Scandinavian boulders to our eastern coast has been frequently 

 discussed in my writings on the Yorkshire drifts ; and it seems 

 almost superfluous to reiterate my opinion that the presence of these 

 boulders does not imply their direct transport across the North Sea 

 basin by land-ice. I was convinced by my prolonged examination 

 of the Basement Clay of East Yorkshire that the invading ice-sheet 

 had ploughed up a sea-bottom already strewn with boulders from 

 the shores, — " wherefrom it follows that we must not place much 

 confidence in the evidence gleaned from its erratics as to the actual 

 direction and distance which the ice-sheet has traversed." 



