E. Hull — General Relations of the Drift Deposits. 297 



little terrace of very coarse gravel, wliich appears to be either a 

 river-terrace or the remains of a raised sea-beach. This terrace 

 rises eight feet above high-water mark. 



Fig. 2.— Section at A, in Fig. 1. Fig. 3. — Section at B, in Fig. 1. 



Outcrop of the Upper and Lower Boulder- 

 Clay (1 and 3), with the Middle Sand 

 and Gravel (2) hetween. 



Upper Boulder-Clay (3) resting on Middle 

 Sand and Gravel (2). 



To the North of the Martello Tower, the Upper Boulder-clay 

 again appears, now rising Northwards in the direction of the high 

 ground of Killiney Hill ; and from beneath this the sand and gravel 

 (Fig. 3), which in its turn is succeeded by the Lower Boulder-clay 

 (Figs. 4 and 5), resting upon granite, under Mount Malpas. 



Fig. 4. — Section at C, in Fig 1. 



Fig. 5. — Sketch near C. 



2. Middle sand, etc., resting on Lower Boulder- 

 clay (1), with a basis of Granite (G). 



1 . Lower Boulder-clay resting on 

 Granite (G) shore of Killiney Bay. 



Here, then, on both sides of a synclinal, we have the three divi- 

 sions of the Drift series very clearly developed, but requiring the aid 

 of some previous knowledge of other districts, in order to the eluci- 

 dation of their relations to one another. 



It is altogether unnecessary that I should refer to the order of 

 succession of the Drift deposits further South, as, for instance, in Co. 

 Wexford, after the able observations of previous authors, amongst 

 whom may be especially mentioned Sir H. James, Prof. E. Forbes, 

 and, most recently Prof. Harkness, in the paper already referred to. 

 Suffice it to say that the superposition of the upper and middle divisions 

 (Manure gravel) is there clearly maintained, and is in accordance 

 with the an'angement of the strata in the district here described.^ 



Central Plain of Ireland. — The superposition of the Middle Drift 

 (Limestone Gravel) on the Lower Boulder-clay is of common occur- 

 rence over the central plain of Ireland, though the presence of the 

 Upper Boulder-clay has hitherto not been noticed. This is probably 

 only because it has not been looked for; but, unquestionably, the 

 principal cause of its general absence is recent denudation. That it 

 once had a very general distribution over this area, from which it 

 has subsequently been swept by both marine and atmospheric agents 

 of waste, is a view which I very strongly hold. 



One reason for this belief is the occurrence of large boulders of 



limestone and other rocks, which may be frequently observed strewn 



along the summit or sides of the Eskers. Now, without entering 



into the vexed question of the origin of these remarkable ridges, 



^ See Prof. Harkness's paper already quoted, p. 294. 



