7 12 Proceedings of the Royal Irish Academy. 



colour than the rest of the drift below. The boulder-clay of the western 

 cliff section at Inishlyre, which is 40 feet in height, is similar in type 

 to that of Dornish More and Dornish Beg, and the material at the base 

 of the cliff is finely laminated like the lower boulder-clay of Old Head. All 

 the drift in these islands appears to have been laid down from the eastern 

 glacier, and there is nothing on the ground at the head of Clew Bay to 

 indicate that the southern ice from the Iar-Connaught snow -field passed 

 northwards, as it must have done, over the district lying round "Westport and 

 Xewport. In addition to the uniformity of the drift material of this area, the 

 trend of the drumlin ridges is in the path of the glacier that moved towards 

 the west. They show no signs of having been disturbed by a subsequent 

 northerly ice-flow, but farther east in the Castlebar district the drumlin ridges 

 have their long axes pointed north and south, at right angles to those at the 

 head of Clew Bay (see Plate IV}. Mr. Kilroe 1 suggests as an explanation of this 

 phenomenon, that the Croagh Patrick mountain range shielded the Westport 

 region from the ploughing action of the southern ice, while, farther to the 

 east in the open plain, the boulder-clay already deposited, being fully exposed 

 to the action of the later glacier, was swept northwards by it and was 

 replaced, as in the Castlebar area, by drumlin ridges whose axes are oriented 

 in a direction a little to the east of north. Instead of this more obvious 

 explanation, Kinahan and Close 2 express the opinion that the ice moved 

 landwards over the site of Xewport, ' notwithstanding a little difficulty about 

 the boulder-clay stones of that vicinity,' while at the same time the ice a little 

 farther south moved seawards into Clew Bay, This latter part of the ice- 

 current they believed to be a deflection of the glacier from the south, which 

 curved round on the lee side of the Croagh Patrick range of hills, but, 

 farther north, encountering another barrier at the other side of the bay, was 

 compelled again to flow north-eastwards to join the other portion of the 

 southern stream which moved northwards over the Castlebar district into 

 Killala Bay." 



The foregoing descriptions of the movements of the two principal ice- 

 currents that glaciated the Clew Bay district will enable us to understand 

 the origin of the drifts which encumber a considerable portion of the surface 

 of Clare Island. 



Glaciatiox of Clabe Island. 

 Marks of glacial action can be traced on many of the uncovered rocks of 

 the island. Striae are not of very frequent occurrence, many of the soft 



1 " Soil Geology of Ireland," p.. 143. 



■ " The General Gtacialion of Iar-Connaught and its Neighbourhood in the Counties of Galway 

 and Mayo." p. 13. 



