790 SoLLAS — A Map to show the Distribution of Eskers in Ireland. 



The connection of the eskers with the inland ice is, according to this author, 

 more definitely shown by the following : — 



1. The generally close correspondence between the direction of eskers and 

 that of glacial striation. Both are related to the direction of the flow of the 

 inland ice, and thus to the general slope of the land and its great valley systems. 

 At the same time they may be independent of minor, but still considerable, 

 inequalities of the ground. 



2. The not uncommon transition, which may be traced between esker material 

 and boulder clay, within the same system of eskers, or even within a single esker ; 

 in the latter case usually towards its highest-l3ang end. 



3. The occurrence of great perfectly angular blocks of stone on, or within, the 

 esker ; or even of a superficial covering, not unlike tei-minal morainic material. 



4. The occm'rence of marked dislocations within the esker. 



While these characters indicate a connection with the ice, there are others 

 pointing no less clearly to the influence of running water ; but not of the sea, as 

 is shown by : — 



1. The absence of marine shells from the kernel of the esker, which is some- 

 times beautifully stratified. 



2. The common occurrence of false bedding, which rarely appears in the 

 evidently marine deposits. 



3. The rarity of stratified sheets overlying the kernel of the esker. 



The notion that eskers might be of marine origin was suggested by their form, 

 which appears to require the agency of some force acting at right angles to the 

 direction of their length. 



What is required is — 



1. Running water acting with considerable force, and for a sufficiently long 

 time. 



2. A force acting at right angles to the direction of the esker. 



Nothing but a melting ice-sheet can give us this. 



The author then turns to Greenland, and cites Nordenskibld to show that deep 

 crevasses occur in the ice, and that considerable streams of water flow beneath it ; 

 and that its surface is undulating. The crevasses arise in consequence of the 

 movement of the ice, and are greatest where the movement is most rapid ; they 

 run at right angles to the direction of movement ; they are deepest in the middle 

 of a flow, and diminish towards the sides. 



As regards the bottom of an ice-flow, we know that tunnels exist there, 

 produced by the action of air and water ; and these may be quite general beneath 



