SoLLAS — A Map to show the Distribution of Eshers in Ireland. 819 



to call this over-cast bedding, since it appears to be due to the casting down of 

 sediment over a steep slope ; the material sometimes lies at a high angle. 



At the base of some eskers horizontally bedded sands and gravels are often met 

 with, and, in one instance, as pointed out to me by Mr. Praeger, in the Greenhills 

 esker, near Dublin, this was seen to be beautifully ripple-marked. 



What are evidently disturbances of the bedding, produced subsequently to its 

 formation, are far from uncommon. In the Greenhills esker, close to Timon Castle, 

 Dublin, a particular bed of pebbles can be traced along a horizontal course for a 

 considerable distance ; but at one place this is interrupted for an interval of about 

 30 feet ; fragments of it, however, are clearly visible lying along an irregular 

 curve beneath a mass of disorderly sand and gravel. Cavings in, such as this, 

 suggest that blocks of ice become buried up within the esker, and by their subse- 

 quent melting the overlying material was deprived of support. 



Faults are not uncommon, contortions are frequently, and reversed faults 

 occasionally, met with. Mr. Close informs me that a good instance of a reversed 

 fault was jDointed out to him by Mr. F. J. Foot in a cutting through an esker on 

 the right-hand side of the road going from Boyle, to Moj^gara, about four and 

 a-half miles due west of Boyle, which is in county Roscommon. The settling of one 

 side of the ice on one side of the esker might produce a thrust sufficiently powerful 

 to produce a fault of this kind ; it does not necessarily imply that the whole glacier 

 was still in a state of flow. 



The large blocks of stone resting on the surface of an esker, and sometimes 

 included within it, to which the officers of the Geological Survey so frequently call 

 attention, are readily explicable as morainic fragments left behind in the last stages 

 of the retreat of the ice. In common with many other phenomena they suggest 

 that the eskers on which they occur were deposited rather in tunnels than in open 

 valleys of the ice. 



Not at all infrequently a core of coarse and confusedly arranged material is 

 found within a mantle of exquisitely stratified sand and gravel, which may be 

 repeatedly faulted. 



From all that I have seen of the structure of eskers, I should certainly conclude 

 that in most cases they have been deposited on the place where they are now 

 found by the action of running water, and that they have not been precipitated in 

 mass from the bottom of sinking ice-canons. 



A great number of observations on the direction of glacial striae over many 

 parts of Ireland have been recorded by the officers of the Geological Survey ; but 

 the most important systematic study of these and other indications of the move- 

 ments of the glaciers of the Pleistocene Period, we owe to the Rev. Maxwell Close, 

 whose Paper on the subject we have referred to above, p. 787. Mr. Close describes 

 (i.) a system of rock scorings, which show the direction taken by the ice at the 



