SOFTH LANCASHIRE, CHESHIRE, AND THE WELSH BORDER. 381 



sionally to pass horizontally into gravel. Yet the essential charac- 

 teristics of the two deposits are sufficiently preserved to make a 

 broad separation possible — the sands and gravels consisting of water- 

 worn stratified materials and rising into ridges and hummocks, 

 while the Boulder-clay contains scratched stones, is scarcely or not 

 at all bedded, and has a tendency to lie in hollows. The drifts of 

 the two districts therefore, though lithologically different, are quite 

 analogous in their arrangement, and are probably the result of a 

 similar, if not the same, sequence of events. 



As a general conclusion from the facts detailed above, it may be 

 stated that : — 



1. The stria? on the English and Welsh sides respectively, while 

 showing variations among themselves, by a marked preponderance 

 in one quarter of the compass, indicate a direction of principal gla- 

 ciation, this direction being, on the English side from about I^.N.W., 

 and on the "Welsh from about W.S.W. 



2. The direction of glaciation in both districts agrees very closely 

 with that of the transportation of the drift, but is only locally in- 

 fluenced by the form of the ground. 



3. The striae are by no means universal, but are found almost 

 exclusively in connexion with those beds in the drift which contain 

 evidence of the actual presence of ice. 



Part III. 

 Origin of tlie Strict. 



Yarious theories have been x^ut forward to account for the origin 

 of the striae in South Lancashire. Mr. Morton at first suggested 

 the hypothesis of an ice -sheet moving from S.E. to iST.W., but sub- 

 sequently saw reason for abandoning this theory in favour of ice- 

 fields carried by tidal currents *. Mr. Tiddeman, after describing 

 the glaciation of Xorth Lancashire, infers from the general paral- 

 lelism that the striae of North and South Lancashire were due to 

 the same cause, this cause being the movement of an ice-sheet from 

 N.N.W. to S.S.E.t Mr. Mellard Eeade accounts for the cross striae 

 on the hypothesis of ice-sheets moving from the mountains of Cum- 

 berland and Wales respectively, and varying in relative power J. 

 Mr. De Ranee attributes the glaciation to an ice-sheet moving 

 southwards during the period of the Till, and before the submergence 

 of the Boulder-clay period §. Sir Andrew Bamsay, in 1876, ascribed 

 the glaciation of Anglesey and the scooping out of some shallow 

 valleys to the grinding power of a vast glacier, moving from the 



* Proc. Livei'pool Geol. Soc. sess. 18, 1876-77. 



t Quart. Journ. Geol. Soc. vol. xxviii. (1872). 



X Proc. Liverpool Geol. Soc. sess. 14, 1872-73. 



§ Geological Survey Memoir on the Superficial Deposits of S.W. Lancashire. 



