336 ANNUAL EEPOKT SMITHSONIAN INSTITUTION, 1917. 



the underlying estuarine clays. In the Bann Valley the Thracia clay 

 was removed and brownish river sand deposited in its place. Else- 

 where on the coast the Thracia. clay is overlain by blown sands. 

 This elevation carried the land about 6 feet above its present level, 

 and the final subsidence has resulted in the accumulation along the 

 shore of black littoral clays ("slobland"), crowded with My a are- 

 naria, Cardium cdule, and Mytilus edulis. At Belfast their thickness 

 is 6 feet G inches. 



Nowhere else in Ireland have we a section approaching this in 

 completeness. All round the coast drowned and alluvium-filled val- 

 leys, submerged forests, and " slobland " point to a postglacial sub- 

 sidence, which at Cork must have exceeded 50 feet. At many points 

 on the west coast, peat beds with tree stools in situ can be seen to pass 

 below low-water mark. But in the absence of more complete sections 

 it is very difficult to "place" these deposits in the postglacial se- 

 quence. 



Near Dublin the 15-foot beach (i. e., 25-foot beach of Belfast) lies 

 on submerged peat, and is therefore younger, as in Ulster. In the 

 estuary of the River Slaney, County Wexford, Kinahan (1875) de- 

 scribed the following section: 



Mud, 16 feet ; surface at sea level. 

 Peat, 5 feet. 



Gray muddy stuff, 1 foot 5 inches. 

 Marl (bowlder clay). 



The peat shows that the land must have stood at least 30 feet 

 higher than at present, and this is confirmed on the neighboring sea- 

 coast. No particulars of the "gray, muddy stuff " are given, but pos- 

 sibly it corresponds to the gray sand of the Belfast section. The 

 "mud" corresponds to the estuarine clays and overlying deposits; 

 near the end of the time when it was accumulating there seems to 

 have been a slight rise of the land, as the upper stratum is highly 

 impregnated by iron and separated from the lower by a layer of 

 shells. 



It is difficult to correlate the superficial formations of the interior 

 with these estuarine and marine deposits, owing to the lack of com- 

 mon elements. Here again the cold period represented by the later 

 corrie and valley glaciers offers a useful horizon. This is well seen 

 in the Ballybetagh bog, near Dublin, described by Mr. W. Williams 

 (1878). The section is as follows: 



6. Peat with oak and alder, 2 to 3 feet. 



5. Grayish .clay, 2$ to 3 feet. 



4. Brownish clay, with Cervus megaceros and plants, 3 to 4 feet. 



3. Yellowish clay, largely composed of vegetable matter. 



2. Fine, tenacious clay, without stones. 



1. Bowlder clay. 



