T. Mellard Reade — Glacial Geology. 311 



On commencing the inquiry I had no idea whither my observa- 

 tions would lead me, and had no prepossessions, I quickly found, 

 however, that 1 came into collision with one of the prevailing views 

 — I had almost said dogmas — of the day. 



The drift of the north-west of England had been arranged in 

 a tripartite series consisting of, in ascending oi'der. Lower Boulder 

 Clay, Middle or Interglacial Sands and Gravels, and Upper Boulder- 

 clay. My observations led me to believe that there were no suf- 

 ficient grounds for such a geological division, and that the whole of 

 the drift deposits were one glacial series from top to bottom. This 

 view is now the one generally adopted, and also as I understand 

 by the new school of glacialists who ascribe these deposits to the 

 ploughing up of the Irish-Sea bottom by land ice. And this brings 

 to my mind the fact that there has been a concurrent change of 

 position on the part of the land-ice glacialists, for the old school 

 believed in the occurrence of several interglacial periods and thought 

 they could read the record of them in the deposits. 



Until lately the preponderance of opinion among geologists who 

 have studied the subject in the field was that the glacial deposits of 

 the north-west of England were sea-bottom in situ and that the 

 high-level sands and gravels indicated a submergence of the land 

 in glacial times to at least 1400 feet. 



The late Mr. Belt struck a new note when he boldly declared his 

 belief that the high-level drift of Moel Tryfaen, in Carnarvonshire, 

 had been pushed up into its present position by a sheet of land-ice 

 traversing the Irish Sea.^ Mr. Belt was listened to by few at the 

 time, but in the whirligig of time he is now having ample revenge. 



The late Professor Carvill Lewis, fresh from his experiences in 

 America, revived this idea of Belt's in a modified form, and he also 

 met with much opposition. Since his death the idea has fructified, 

 and we now have an energetic band of geologists who are bent on 

 nothing less than raising what was considered at first to be a " wild 

 idea" into a geological dogma. 



Whether there has been justification for this veering round of 

 geological opinion it will be our object presently to inquire. In the 

 meantime it is sufficient to suggest that it is not the province of 

 geological enquiry to search out facts with the object consciously 

 or unconsciously of running a theory, yet this is one of the many 

 pitfalls against which geological reasoners have to be constantly on 

 their guard. 



The Glacial Drift of the Irish-Sea Basin and its System of 



Distribution. 



Low-Level Boulder-clay and Sands. 

 The whole of the plains of Lancashire and Cheshire are, with 

 the exception of local patches, covered with a mantle of Boulder- 

 clay and sands of varying thickness, from a few feet in the more 

 exposed localities to 160 feet in the deeper river channels. Both 

 the clay and sands generally contain remains of mollusca in a more 

 or less fi'agmentary condition. 



1 Nature, vol. x. pp. 25, 26, 1874. 



