SHEPPARD : INTER-GLACIAL GRAVELS OF HOLDERNESS. 13 
to one hill having been flattened out. Swamp hollows are enclosed 
amongst these hills.''' 
A few words may not be out of place here on the subject of the 
vexed question of a marine submergence during an inter-glacial mild 
period. In the first place the fact that these gravel mounds repeat 
the features of and are a continuation of the moraine of Flambro' 
Head is a strong argument against their marine origin. The inter- 
calation of boulder clay, a material quite unlike any modern marine 
deposit of the Arctic seas, is another fact which tells strongly against 
this hypothesis. Then there are tlie further difficulties that no 
beaches or marine deposits have been found on the Chalk-wolds, or in 
the country west of the Wolds, where they should occur on the 
assumption of a submergence. 
It may be noted that Mr. Clement Reid recognised this difficulty 
when he put on his map of Inter-glacial Holdernesst the words " No 
fossiliferous marine gravels yet known over this area." I have 
italicised the word " yet " for Mr. Reid seems to imply that such 
gravels probably exist though they have not yet been found. It does 
not appear to me probable that after the mapping of the whole area 
both for Drift and Solid by Mr. Reid and his colleagues, together 
with the careful work of many other observers, has failed to detect 
any sign of marine action, that there is much probability in the sug- 
gestion that marine fossiliferous gravels will be found. The hills of 
the Burstwick range have the disposition, composition, and contents 
which have been described as characterising other moraines, and 
saving the occurrence of shells they have none of the features of a 
marine deposit. 
As to the shells themselves, I am given to understand that 
saving Corbicula fluminalis they constitute a fairly natural assem- 
blage, but their condition is conclusive proof that they did not live 
where we find them, and the many evidences which have been 
described by Mr. Lamplugh, Mr. Reid and others, of the transport of 
shells by glacier-ice and their inclusion in morainic deposits, justifies 
me in rejecting them as evidence of the marine origin of these deposits. 
See Kendall's Glacial Geology of Isle of Man, Yn Lior Manninagh, vol. i. 
No. 12, p. 9, 1894, for definition of terminal moraine of an ice-sheet, 
t Geology of Holderness, p. 65. 
