iS93. SHELLY-SANDS AND GRAVELS. 425 



levels of a similar nature, indicating a wide extension of these deposits 

 penetrating into the northern parts of the \\'icklow Mountains. 



Other minor discoveries of shelly-sands, gravels, and clays have 

 been made at various localities and at varying heights, but the 

 purport of this paper is to deal with the prominently High-level 

 Shelly Drifts, as bearing upon the two opposing theories of their 

 origin. 



Premising that I speak from personal observation of all the 

 deposits the history of whose discovery I have briefly sketched out, 

 I may say that, discounting local conditions, they have all certain 

 characteristics in common. They are these — 



1. The rocks and materials of which they are composed are 

 largely foreign to the locality, but mixed to a greater or less extent 

 with local materials. 



2. Some of the rocks are far travelled and from different 

 directions, but generally from a northerly direction. 



3. The foreign materials are often above the level of their 

 parent rock. 



4. The pebbles, boulders, and small gravel are to a considerable 

 but varying extent well rounded, a few are striated, some planed. 



5. The sands have often all the aspects of marine sands con- 

 taining a very large proportion of polished and rounded quartz grains. 



In cases where local material preponderates, or materials which 

 may have only travelled a few miles, as at Ballyedmonduff, highly- 

 polished quartz grains are often disseminated through the mass, and 

 can be obtained by washing and riddling. 



6. As their name indicates, these sands and gravels contain sea- 

 shells, mostly in a fragmentary condition, but often well preserved, 

 especially the gasteropods. In fact, shells in any gravelly beach 

 present the same aspect. The fragments are frequently worn at the 

 edges, and microscopic grains of shell-fragments can be obtained by 

 washing, and distinguished by the aid of the microscope. 



7. The local rocks and gravelly materials are frequently angular, 

 though sometimes well rounded — they are, as a rule, more angular 

 than the travelled materials. 



8. The gravels and sands are often well bedded, commonly 

 current-bedded. 



9. In some cases these characteristic marine beds are underlaid 

 or overlaid, or both, with characteristic glacial till, composed almost 

 wholly of local rocks and materials that have come down from a 

 higher level. Moel Tryfaen is the only case in which I have seen this 

 phenomenon, but I have no doubt there are others could we bare the 

 ground. It can only happen in localities where there are high 

 mountains near, commanding the site of the beds. 



10. Finally, the whole aspect of the shelly-sands and gravels is 

 that characteristic of aqueous deposits. 



There are other high-level sands and gravels which, though no 



