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Geological Relations of the East of Ireland. 
§ 163. The rocky coast, called Rob’s Walls, on the south side 
of Malahide bay, consists wholly of floetz limestone, abounding in 
entrochites, madreporites, and other organic remains. The strata 
exhibit four or five great undulations from north tb south, in which 
the highest angle is about 40° and the lowest 5° ; the general range 
being nearly east and west, or more precisely, between 15° south of 
east and north of west, and 10° north of east and south of west. 
§ 164. Floetz limestone sweeps round the western foot of 
Howth, from the strand below the town on the north, to Sutton 
on the south side ; the bluish grey being in both cases associated 
with the yellow magnesian limestone. The martello tower, below 
the town of Howth, stands on beds of limestone gravel and sand 
fifty feet deep* Beneath this alluvium, we perceive bluish and 
blackish grey limestone, in strata, abounding in entrochites, coral- 
lites, and bivalves, ranging 18° east of north and west of south, 
and dipping 13° toward the west. High banks of alluvium line 
the south side of the new harbour, and within the basin rocks of 
magnesian limestone protrude ; but to the west of the western pier 
are crags of bluish grey limestone irregularly intermixed with the 
magnesian, the one stone being frequently enveloped by the other. 
They extend as far west as the Black Rock, which is visible only 
at low water; and beyond them, grey limestone is alone to be 
seen, appearing in the banks under the soil, in strata, two and three 
feet thick, dipping toward the north-west at an angle of 25° 
-to 30°. But more inland, in the quarry below the public road, 
they dip 40° toward the same quarter. 
On the south-west side of Howth, near Sutton, the grey and the 
magnesian limestone appear to be interstratified, and also irregularly 
intermixed, with a slight inclination toward the south-west; the 
Vol. V. 2 L 
