Correspondence — Professor J. W. Gregory. " 191 



that the banks south of Ilkley somethnes rest on boulder clay ; 

 if that be the case with the Delves it would be strange if some 

 Carboniferous Limestone material had not been included in that 

 bank. In a much shorter examination of the mounds further east 

 I saw plenty. 



These objections to the morainic origin do not apply to the 

 explanation of the Lanshaw Delves, which seems to me probable. 

 The bank strikingly reminded me of some Scottish corrie moraines. 

 In suggesting this explanation I did not deny either the former or 

 contemporary existence of ice to the north of it, by which the drift 

 mounds may have been formed as the lateral moraine of a Wharf e- 

 dale glacier. On that question I have expressed no opinion. What- 

 ever the origin of the mounds I regard the Lanshaw Delves as a later 

 and more local formation. 



I am obliged to Professor Kendall for calling my attention to the 

 account of the Lanshaw Delves in the valuable jiaper by Jowett 

 and Maufe ; he remarks that my omission to quote it is 

 unaccountable. I may therefoie explain that in looking up the 

 literature I trusted till the year 1914 to Shepherd's valuable 

 bibliography ; not finding any reference in its index to Lanshaw 

 Delves, I examined the papers dealing with Ilkley and the valley 

 of the Wharfe ; but as Messrs. Jowett and Maufe's paper was 

 entitled " The Glaciation of the Bradford and Keighley District ", 

 I did not expect to find any account of the Delves in it. I am glad 

 to find that according to Messrs. Jowett and Maufe the top of the 

 moor near the Lanshaw Delves was never covered by ice, and that 

 they had already identified the Lanshaw Delves as a moraine. 



The one formation in England for which there was high authority 

 for identification as a " high level esker " (Moel-y-Crio, which is in 

 North Wales, is so fragmentary that the case for it was less definite) 

 is shown by Professor Kendall's article to be now unanimously 

 accepted as a moraine, and the problem of the English eskers is 

 thereby much simplified. 



In regard to the drifts on the Aire Valley I agree with Pro- 

 fessor Kendall that my paper gives no full account of them. It 

 merely records facts which led me to agree with the Geological 

 Survey Memoirs that these " gravel mounds " (e.g. Geol. Surv. 

 Mem., 92, S.E., p. 12) were dej)osited in water. 



In the case of the York and Escrick drifts it is unnecessary 

 to follow Professor Kendall's summary of the history of the morainic 

 theory. He misquotes me as describing " the two ridges as con- 

 sistmg of sand and gravel ". I made no such statement. The remark 

 Avhich Professor Kendall has misquoted is that " Two curved bands 

 of glacial sands and gravels occur . . ." ; they occur upon the ridges 

 which, as is clearly shown in the Geological Survey maps, consist 

 mainly of boulder clay. Boulder clay does not form kames and 

 osar ; the possibility of those formations occurring near York is 

 restricted to the bands of sand and gravel. 



