i9iS. Hiscn. -The Iriali Sea Glacier. 6i 



view that a Lower and Upper Boulder-clay with intermediate 

 Sands and Gravels was proven, and the efforts to lit in ob- 

 served facts in the field with this dominant theory confused 

 and hampered field-work for many years. The most 

 important section in the Irish Sea area is that of Killiney 

 Bay, lying between Dalkey and Bray. For many years 

 these deposits were accepted as affording definite proof 

 of the three-fold nature of the Drift, and it was only in 

 1896 that opinion began to move away from that standpoint. 

 During the years 1894 and 1895 Prof. Sollas and Mr. R. LI. 

 Praeger worked at the glacial deposits of this district and 

 brought forward the importance of the part played by ice 

 from the north and north-east. Attention was drawn to 

 the abundance of shells, fossils and erratics (basalts, chalk, 

 flints, Ailsa Craig rock) of northerly origin, and while the 

 authors retained a modified view of submergence to account 

 for the broken condition of the shells, they considered the 

 main mass of the material present to have been brought 

 by ice from the north and north-east rather than from the 

 north-west, as early investigators had asserted. 



For some years opinion on the subject drifted about 

 from point to point in a state of indecision. In 1901 the 

 new Drift Survey of Ireland was undertaken by the Geo- 

 logical Survey of Ireland, and under the Directorships of 

 Mr. (r. W. Lamplugh and Prof. Cole a selected number of 

 districts have been surveyed. These investigations destroyed 

 the earlier theory of a considerable submergence and reduced 

 the interglacial period to the local uncovering of a area — an 

 interglacial period such as may have taken in the South of 

 Ireland during the time which elapsed between the decay 

 of the western lobe of the Irish Sea Glacier and the advance 

 of the ice-sheet from the interior of Ireland. 



The theory advanced by Lamplugh that the glaciation 

 of western Europe proceeded successively from east to west, 

 so that an easterly ice-sheet might have begun to decay 

 before a more westerly ice-sheet had reached its maximum, 

 gives a certain amount of assistance in solving this question. 

 According to this theory the maximum development of the 

 ice-sheet of central Ireland would be later in time than the 



