194 The Irish Naturalist. 



NOTES ON GLACIAL DEPOSITS IN IRELAND. 



BY PROFESSOR W. J. SOLLAS, F.R.S., AND R. LLOYD PRAEGER, B.E. 



I. — The Bray River. 



( Concluded from page 1 66.) 



Crossing the bridge at Enniskerry, and turning back towards 

 Bray down the northern side of the stream, we find a steep 

 wooded slope rising above the stream-bed to a height of per- 

 haps ioo feet. This is formed of glacial deposits from foot to 

 summit, the lower half, roughly speaking, being boulder clay, 

 the upper half boulder gravels. Sections are few, and the 

 beds where seen are very similar in character to those on the 

 other side of the river, which have just been described ; we 

 therefore pass them by, and proceed to the interesting ex- 

 posures, not yet dealt with, which occur on the southern bank 

 between Bray and Dargle bridge. Leaving Bray, we cross the 

 end of a little valley where a streamlet has cut through the 

 drift to a depth of fifty or sixty feet, and find our first section 

 in a wooded bank which overhangs the stream ; the base of 

 the section is but a foot or two above the level of the river, 

 which here flows through a flat alluvium-filled valley to the 

 sea, with steep bluffs of drift rising boldly on either bank. In 

 our first section (fig. 4) we find twelve feet of red boulder clay 

 succeeded by a conglomerate of boulder gravels. In places 

 the boulder clay is clearly laminated ; at one spot fourteen 

 alternating horizontal layers were counted in a height of six 

 inches, the different laminae being distinguished hy the pre- 

 dominance of sand or clay ; while a band of small pebbles, 

 some three inches in thickness, was traced horizontally along 

 the cliff for a distance of thirty to forty feet. The stones in the 

 boulder clay are for the most part small (one inch in dia- 

 meter), but a few are one to two feet across ; they consist 

 chiefly of Carboniferous limestone. Cambrian quartzite, and 

 granite. The flatter stones lie parallel to the lamination planes ; 

 the larger and more irregular fragments lie in no particular 

 direction. A careful examination of this laminated clay re- 

 vealed no indication of shearing having taken place, and the 

 stratification appeared such as could only be produced by 

 deposition in water. Fragments of marine shells are frequent. 

 The clay becomes a little more stony towards the top, and is 



