120 The Irish Naturalist. 



clay were highly polished and rounded quartz grains. Flakes 

 of mica were common. All the residual material was non- 

 calcareous and did not effervesce with acid. 



On and beyond Bray Head to the southward, sands and 

 gravels and boulder-clay of the shelly type continued. At 

 the south side of Bray Head I picked up quite a number of 

 pebbles of red Triassic sandstone which corresponded precisely 

 with the New Red Sandstone at Newtownards in County Down. 

 We have now rapidly traversed the coastal deposits of drift 

 with a glance at a bed of clay a little inland. It remains to 

 follow the drift of the valleys to the high-level developments 

 on the Three Rock Mountain and elsewhere, but before doing 

 so let us ascend the Great Sugar-Loaf. Starting from the 

 top of the Glen of the Downs we note the presence of granite 

 boulders lying on the side of the mountain between the level 

 of 1,000 and 1,100 feet. These, it is needless to say, are erratics, 

 as the Great Sugar-Loaf is of Cambrian quartzite. At about 

 1,100 feet the talus of the quartzite cone forming the summit 

 begins, so that if any granite boulders ever reached a higher 

 level they would most likely get covered up by the talus 

 material. On the descent to the north-eastward the talus 

 reaches a lower level, and at 880 feet above the sea a granite 

 boulder was observed amongst it. Also at 550 feet one 3 feet 

 in diameter occurred, while still lower down a much larger 

 one almost entirely embedded in the ground was to be seen. 



On the main road from the Glen of the Downs to Bray some 

 very interesting gravel pits in esker-like mounds are to be 

 seen, consisting largely of limestone gravel and boulders 

 intermixed with granite. Shell fragments were found in all of 

 them, but mostly in a very chalky and carious condition, in 

 some cases being a mere net- work. They are mostly indeter- 

 minable excepting Turritclla and Cardium. These mounds 

 show oblique bedding of sand and gravel, in one case capped 

 with boulder-clay. Some of the fine gravel is so clean that it 

 runs like shot on being disturbed. We will now turn our 

 attention to the valleys, and first of all that of Glennasmole 

 enlists our sympathies, due to some extent to the splendid 

 conditions of weather under which it was explored. Again we 

 were indebted to Mr. Close's guidance and to Mr. Praeger's 

 help. 



A drive by the banks of the River Dodder showed a fine 

 series of river terraces formed out of the glacial drift. At a 



