ANCIENT GLACIERS IN EASTERN HEMISPHERE. 145 



" The Confluent Glaciers. 



" With the growth of ice-caps upon the great centres 

 a condition of affairs was brought about in the Irish Sea 

 productive of results which will readily be foreseen. The 

 enormous volumes of ice poured into the shallow sea 

 from north, south, east, and west, resulted in such a con- 

 gestion as to necessitate the initiation of some new systems 

 of drainage. 



" The Irish Sea Glacier. — The ice from Galloway, Cum- 

 bria, and Ireland became confluent, forming what the late 

 Professor Oarvill Lewis termed ' the Irish Sea Glacier/ 

 and took a direction to the southward. Here it came in 

 diametrical conflict with the northward-flowing element 

 of the Welsh sheet, which it arrested and mastered ; and 

 the Irish Sea Glacier bifurcated, probably close upon the 

 precipitous Welsh coast to the eastward of the Little 

 Orme's Head, and the two branches flowed coastwise to 

 eastward and westward, keeping near the shore-line. 



" The westerly branch swept round close to the coast in a 

 southwesterly direction, and completely overrode Anglesea,; 

 striating the rock-surfaces from northeast to southwest 

 (see map), and strewing the country with its bottom-mo- 

 raine, containing characteristic northern rocks, such as the 

 Galloway granites, the lavas and granites of the central and 

 western portions of the Lake District, and fragments of 

 shells derived from shell-banks in the Irish Sea. One epi- 

 sode of this phase of the ice-movement was the invasion 

 of the first line of hills between the Menai Straits and 

 Snowdon. The gravels and sands of Fridd-bryn-mawr, 

 Moel Tryfaen, and Moel-y-Cilgwyn, are the coarser wash- 

 ings of the bottom-moraine, and consequently contain such 

 rock-fragments and shells as characterise it. From Moel- 

 y-Cilgwyn southward, evidence is lacking regarding the 

 course taken by the glacier, but it probably passed over 

 or between the Rivals Mountains (Yr Eifl), and down 



