Chaiji.eswoutii — Glacial Geologi/ of Nor th-Wcst of Ireland. 219 



over Iiiishoweii, down the estuary of the Foyle, and along the edge of the 

 basalt plateau, made its inlluenee felt as far as I slay. 



11. The Bamesmore Granite lioidder Dispersal. 

 The boulders of Earnesniore granite in the drifts of N.-W. Ireland are 

 usually very well rounded, more rarely sub-angular, and only occasionally 

 polished or striated. In size they vary within considerable limits ; their 

 average diameter is roughly one foot. 



Fig. 1. 

 Mup illustrating the (listiibiilioii of granite boulders in the north-west of Ireliiiul. 

 if denotes the outciup of the Baniesjiiore granite ; B, that of the Done;;al 

 granite; T, that of the granites of Tyrone. The dotteJ areas lepresent the 

 country covered by granite boulders. The dasli line repiesents the limits of 

 tiie Donegal granite houl.Ier dispersal ; the dot and dash line these of the 

 Earnesniore dispersal ; the dot line those of the Tyrone dispersal; dash and 

 two-dot linis indicate the W. limit of tlie Scottish ice. Airows indicate the 

 direction of ice-flow. Scale — 25 miles = 1 inch. 



A striking proportion of them occur on the surface of the ground, a small 

 percentage only in the drifts. This singular mode of occurrence attracted 

 the attention of the earlier writers, who attributed it to the agency of 

 " floating ice during the submergence of the country beneath the sea, when 

 the stratified drift and eskers were formed, and after the time of the 

 production of drumlins and rock-striations.^ 



It is intended in the following to describe briefly the approximate limits 



I M. Close, Jouin. Roy. Geol, Soc. Ireland, 1866, p. 229. 



