On the Physical Geology of the Neighbourhood of Dublin. 158 
about Foxrock, and Dalkey, on the Killiney Hills, &e. It is 
often strikingly displayed on limestone freshly bared for quarry- 
ing; though, of course, almost immediately removed. There was 
a very fine example of this in a quarry near Finglas Bridge (the 
one in which the beds are nearly horizontal). The abrading 
agent has frequently produced very observable crag-rounding, as 
distinct from mere surface-rounding, though generally accom- 
panied thereby, as on Ireland’s Eye, Shankill, and Bray Head. 
This phenomenon should be viewed from a sufficient distance— 
say from half a mile to a mile and a half—and in the afternoon, 
when the sun is favourably situated for showing the effect, owing 
to the direction of the glaciation. The highest point at which 
the striations can be certainly found is on the very summit of 
Shankill, near the Scalp, 912 feet. Unfortunately the granite 
hills would not preserve the striations except under special 
circumstances, otherwise those marks of ice-action would be 
traceable to much greater heights. 
The Lower Boulder Clay is of the usual weil-known character. 
It is generally a very stiff ciay containing well rubbed, blunted, 
and scratched, though sometimes angular, and very rarely rolled, 
stones and blocks; these are often two feet in length, though 
they are usually much smaller. Except in the 8.E. part of this 
district the great majority of the stones are limestone, even in 
places situated some miles from the edge of the limestone ground. 
As the great ice movement was from the extensive limestone 
plain, we should naturally expect a preponderance of limestone 
blocks in the boulder clay; but it is sometimes very surprising 
that the boulder clay, after having been swept along over two or 
three miles of granite ground, should have picked up so few 
granite blocks as it has done. In such cases the largest blocks 
in the clay belong to the local rock. The upper surfaces of such 
blocks are sometimes ground, smoothed, and scored in the same’ 
manner as the surface of the living rock, and in the same 
direction. 
In the N. and N.W. neighbourhood of Dublin the boulder 
clay has been left in more or less well-defined ridges, which are 
quite distinct from the eskers to be mentioned presently, and 
‘which we shall call drumlins; these are not only parallel with 
each other but also with the rock-striation of their immediate 
