276 Beviews — Geological Survey of Ireland. 



The previous geological literature of tlie neighbourhood is also for 

 the first time discussed, under the heading of ' Bibliography,' and 

 a list of this literature is given in an appendix. The memoir is 

 illustrated by 5 plates from photographs, by R. Welch, of Belfast, 

 and by 21 figures in the text. 



The district included in this sheet lies wholly within the county of 

 Dublin. The city of Dublin is in the centre of the sheet, and its 

 suburbs extend along the shores of Dublin Bay to Dalkey on the 

 south and Dollymount on the north, and also along the Liffey valley 

 westward to Chapelizod. The watering-places of Howth and Killiney 

 lie respectively north and south of Dublin Bay within the sheet, and 

 the islet of Ireland's Eye occurs within its northern margin. 



The southern part of the district is high mountainous ground, 

 rising up to 1,763 feet above the sea at a point called Fairy Castle. 

 There is another summit called Tibradden Mountain, which is 

 1,540 feet; and the better known Three Rock Mountain, everywhere 

 visible from the neighbourhood of Dublin, is 1,479 feet high. A hill 

 called Slieve na bawnoge at the extreme south-west corner is 

 1,265 feet. Of the lower hills, Killing Hill has a height of 512 feet, 

 while the summit of that of Dalkey is 472 feet high, within a quarter 

 of a mile of the sea. The mountains, like all granite mountains, 

 have heavy-looking, gently sweeping summit outlines, their flanks 

 descending gradually but rather steeply on the east towards the sea, 

 and on the north to the plain traversed by the Dodder and the Liffey. 



This plain spreads northwards from the foot of the hills, with 

 gentle undulations of between 100 and 200 feet above the sea, rarely 

 rising above the greater height, and often, especially near the sea or 

 on the margin of brooks and rivers, falling below the lesser altitude. 

 It forms a portion of the central plain of Ireland. In the north- 

 western part of the map, however, north of Finglas, the land rises 

 to a height exceeding 300 feet, and the rocky promontory of Howth 

 has a summit of 560 feet in height. All the north-flowing drainage 

 of the southern hill range is received by the River Dodder, which 

 swerves eastward across the plain to the mouth of the Liffey, after 

 issuing from the mountains through the deep hollow of Glenasmole, 

 a little south of Tallaght. The eastern portion of the range is drained 

 principally by two small streams which flow eastward into Killiney 

 Bay. The Liffey, which has a level of less than 40 feet where it 

 enters the district, brings the drainage from the plains of Kildare 

 into the head of Dublin Bay, into which also runs the lesser river 

 Tolka, with a course parallel to the Liffey, and only one to two miles 

 further north. 



The solid rocks of the district are shaly and massive Carboniferous 

 Limestones, Lower Limestone shales and fine grits, Lower Silurian, 

 Bala, and Llandeilo beds, altered Silurian grits and shales, Cambrian 

 quartz rock, granite and basaltic andesites. 



The memoir deals with (1) the solid geology; (2) the 

 palseontology ; (3) the petrography ; (4) the relation between 

 the external form of the ground and its internal structure, and 

 hereunder to the consideration of Glacial and post-Glacial deposits 



