1912-13.] 659 



high road, a good section of the clay is to be seen. It contains 

 very few stones, but, with them, may be picked out round and 

 fantastically shaped flattish concretions of fine calcareous silt. 

 Stuck fast in this clay, at the time of my visit, was a stump of oak, 

 standing fairly upright, but not I think rooted in the clay. It 

 had evidently been washed into the temporary lake, in which the 

 material here was deposited. 



The clayey material seems to have been washed out of the 

 highly calcareous Boulder-Clay previously mentioned, belonging 

 to the Third Stage of glaciation. It is very near the clay in 

 Aghadowey River, which must have been laid down against a 

 hidden remnant of the glacier once filling the valley; but must, I 

 think, be distinguished from this, not only because of having been 

 deposited at a lower level — 60 feet instead of 100, but also 

 because of its containing the oak stump which is comparatively 

 fresh in its inner parts, apparently of more modern origin than 

 glacial times. The three deposits of clay then would seem to 

 mark gradual lowering of, possibly, a great ice-dammed lake, 

 which once filled this valley at periods when its glacier was 

 melting and disappearing, piecemeal. 



RAISED BEACHES. 



These formations have their features of geological interest, 

 but so much has already been written concerning them, that little 

 need be added here. What is known as the Raised Beach in the 

 Roe Valley, and westward towards Derry, is a piatform ranging 

 from the 25 feet contour line, near the very persistent bounding 

 cliff of gravel within, to about 12 feet above datum on its outer 

 margin, where it descends, by two steps fairly recognizable in 

 certain places, to the level of the reclaimed slob, or former 

 foreshore. The two steps referred to, represent stages of uplift 

 which dried all ; they are, therefore, themselves subsidiary raised 

 beaches, about three feet and one foot above the foreshore, and 

 vary up to 100 and 50 yards in width, respectively where 



