76 Geological Society : — 



same agent that distributed the Boulder-clay, also striated the rock- 

 surface and moved from the north-west. 



Part II. The Welsh Border. 



The striations within the Welsh Border also show a general 

 parallelism, but in a direction E.N.E., the few exceptions that occur 

 being close to the Border. The direction in which the drift has 

 been transported shows a corresponding change ; though analogous 

 in arrangement to the Lancashire drift, it has all travelled from 

 W.S.W. to E.N.E. The boundary between the northern drift of 

 the English side, and the western drift of the Welsh runs approxi- 

 mately along the coast, bending inland here and there, and cutting 

 inland across parts of South Flintshire and Denbighshire. The 

 transportation of the Welsh drift has taken place across the lines of 

 the principal hill-ranges and valleys. Occasionally the two drifts 

 shade one into the other, or are mixed together ; but as a general 

 rule the far- travelled northern drift overlies the more local deposit, 

 and is easily distinguishable by its different materials and by its 

 being comparatively stoneless. 



It may be concluded that : — 



1. The striae 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 

 glaciation, this direction being on the English side from about 

 N.N.W., and on the Welsh from about E.S.E. 



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

 with that of the transportation of the drift, but is only . locally 

 influenced 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 the Strice. 

 The striae are not such as can have been produced by valley- 

 glaciers ; they go across and not down the valleys, nor are there 

 any moraines. The question resolves itself into (1) the hypothesis 

 of two ice-sheets moving in different directions in the two areas ; 

 (2) that of floating ice. The first is opposed by the facts that the 

 rock-surface is not moutonnee on a large scale, and that the striae and 

 terminal curvature are far from universal ; that the drifts associated 

 with the striae are marine deposits; that striae having different 

 directions are found on the same slab. The well-known occurrence 

 of gravel-ore in the drift at the outcrop of a vein is also against this 

 hypothesis. The marine origin of the drifts is indicated by their 

 well-marked stratification as a whole, by the alternations of well- 

 washed sands and gravels with the Boulder-clays, and by the occur- 

 rence through all the beds of marine shells. A lower or basement- 

 clay is seen in places under this marine drift, but it is always the 

 latter with which the striae are associated. The great development 

 of undoubted marine beds and comparative rarity of moutonnee sur- 

 faces constitute the principal differences between this region and 



