Charleswohth — Glacial Geology of North- West of Ireland. 263 



Everywliere tbey consist of sand and gravel and water-worn material. Tliis 

 clear evidence of water action donbtless led the earlier workers astray, lor 

 all tliese features were consistently regarded and described as eskers.^ 



More recently,^ Professor J. "W. Gregory has alluded to these gravel 

 aucnninlations of County Tyrone, lie clearly recognized their marginal 

 formation. He writes : — 



" In 'I'yrone, in the hills to the north and north-west of Pomeroy, is 

 a third group of eskers, formed as glacieluvial marginal deposits around 

 glaciers flowing from the hills" (p. 148). 



His conclusions as to the direction of ice-movement, as evidenced l)y tliese 

 features, are, however, totally at variance with the results here submitted, 

 wliich are based upon a careful examination of tlie drifts, striae, marginal 

 drainage phenomena, &c. Speaking of the moraine along the northern foot 

 of the Evishanoran Mountain (886), he says (p. 1?A) : — 



" It has obviously been formed as a marginal formation due to a 

 glacici- flowing northward and north-westward from Evishanoran 

 Hills." 



He (continues (p. 134) : — 



" The esker near Duunamore was probably similarly due to ice from 

 .Slievemore (842 feet)." 



The following argument seems to clinch the evidence already set forth. 

 'J'he emergence of the main watershed of the Sperrins as an irregular 

 uuuatak, and the shrinkage of the ice down the flanks of tlie hills, as set out 

 above, can only mean that the snow-line hereabout at that time was 

 somewhere in the neighbourhood of ^^,000 feet or more. To suppose tliat 

 glaciers issued from hills only some six miles to the south and some 1,400 feet 

 lower, as is suggested by Professor J. W. Gregory, would lead to hopeless 

 contradiction of levels of snow-lines in this area. 



Water streaming from tlie ice has, without doubt, been the chief agent in 

 the moulding of the morainic material into its present form. Some of these 

 ridges and mounds, e.g., those running along the lower slopes of tlie Beleevna- 

 more Ifange, were formed as true moraines along the edge of the ice above 

 the level of standing water ; others were equally clearly produced by ice 

 standing in ponded waters. Professor Gregory draws a distinction between 



1 Even Professor G. A. J. Cole, in the introductory sketch to his paper on the 

 Igneons Rocks of the Country West of Cookstown, refers to these moraines as tlie 

 "classical eskers" ; and again, in his paper on the Bletamorphic Rocks of this area, 

 already quoted (op. cit.. p. 446), speaks of " The gigantic eskers and gravel mounds." 



2 The Irish Eskers, Phil. Trans. Roy. Soc, Loud., ser. B, vol. 210 (1920), p. 133. 



