ANCIENT GLACIERS IN EASTERN HEMISPHERE. 143 



planation of special points it may be possible to accom- 

 plish a clear presentation of the facts. 



" Wales. — The phenomena of South Wales are com- 

 paratively simple. Great glaciers travelled due southward 

 from the lofty Brecknock Beacons, and left the charac- 

 teristic moutonnee appearance upon the rocky bed over 

 which they moved. The boulder-transport is in entire 

 agreement with the other indications, and there are no 

 shells in the drift. The facts awaiting explanation are 

 the occurrence in the boulder-clays of Glamorganshire, at 

 altitudes up to four hundred feet, of flints, and of igneous 

 rocks somewhat resembling those of the Archaean series 

 of the Wrekin. At Clun, in Shropshire, a train of erratics 

 (see map) has been traced back to its source to the west- 

 ward. On the west coast, in Cardigan Bay, the boulders 

 are all such as might have been derived from the interior 

 of Wales. At St. David's Peninsula, Pembrokeshire, striae 

 occur coming in from the northwest, and, taken with the 

 discovery of boulders of northern rocks, may point to a 

 southward extension of a great glacier produced by conflu- 

 ent sheets that choked the Irish Sea. Information is very 

 scanty regarding large areas in mid- Wales, but such as 

 can be gathered seems to point to ice-shedding having 

 taken place from a north and south parting line. In 

 North Wales, much admirable work has been done which 

 clearly indicates the neighbourhood of Great Arenig 

 (Arenig Mawr) as the radiant point for a great dispersal 

 of blocks of volcanic rock of a characteristic Welsh type. 



" Ireland. — A brief reference must be made to Ireland, 

 as the ice which took origin there played an important 

 part in bringing about some strange effects in English 

 glaciation, which would be inexplicable without a recog- 

 nition of the causes in operation across the Irish Sea. 

 Ireland is a great basin, surrounded by an almost contin- 

 uous girdle of hills. The rainfall is excessive, and the 

 snowfall was probably more than proportionately great ; 

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