804 SoLLAS — A Map to shoio the Distribution of Eskers in Ireland. 



When from this general statement, we pass to matters of detail, unanimity is at 

 an end, and geologists are found occupying two opposing camps, one represented 

 by Hummel and the other b}^ Hoist, with intermediaries who agree with both. 

 The one regards ground-moraine as the source of the material of the esker, the 

 other prefers to derive it from superglacial or englacial drift ; tlie one pictures its 

 deposition in subglacial tunnels, the other in ice canons. 



Much time has been spent in speculative discussion of these points — time not 

 wholly wasted, since the imagination having produced many pictures of what 

 might have occurred, observation has been assisted in its task of more speedily 

 recognising, in the field, those phenomena which are serviceable for explanation. 

 The only observations which we possess, directly bearing on the question, are those 

 of Wright and Russell ; and these agree in referring the place of deposition of 

 eskers to tunnels in the ice, not necessarily at its base, and in attributing their 

 material, at all events to a large extent, to superficial moraine matter. So far as 

 observation helps us, it finds truth in the views of both Hummel and Hoist ; though 

 in both, likewise, some error. The glaciers described by Wright and Russell, though 

 dwindling, are not in the final stages of dissolution ; and thus many important 

 problems connected with the formation of eskei'S still wait for solution: such, in 

 particular, as the remarkable manner in which they run up and down over liills 

 100 to 200 feet in height. 



We now pass to the classification and description of the chief systems of eskers 

 met with in Ireland. For the information on which this is based I am almost 

 wholly indebted to the published writings of my colleagues on the Geological 

 Survey, and the information on the map, also, which this account is intended to 

 explain, is abstracted from the one-inch map)s of the Survey. 



The System of Ballyhaimis. 



This system consists of five principal chains, with several outlying mounds 

 and ridges distributed over the eastern part of county Galway, the west of county 

 Roscommon, and the south of county Mayo. Enumerated in the order in which 

 they are encountered, on proceeding from north and west to south and east, these 

 chains may be named as follows : — 



1. Ballindine chain, with an outlj^ing group of ridges, 



north of Claremorris, in county Mayo. 



2. Dunmore chain. 



3. Tuam chain. 



4. Kilnalag chain. 



5. MoA'ne chain. 



6. NewtowTi-Bellew chain. (All in fig. 2.) 



