238 
Mr. Weaver on the 
greywacke slate, and upon transition rocks. It occurs either in 
unconnected isolated portions, or in extensive mountain masses. 
§ 13 5. The red sandstone conglomerate of Dunabate has been 
already adverted to (§ 122}, where it appears to be in immediate 
contact with transition rocks. Its composition is the same as that 
of the great dyke in Lambay. A perfectly similar rock occurs in 
situ at the northern foot of the hill of Lyons (§ 54), w r here it is 
exposed for about ten fathoms in length, in strata four feet thick, 
ranging east and west, dipping 32° to the north, and resting un- 
conformably on greywacke slate, some of its pebbles being as large 
as half the head. The strata no doubt underlie toward the north 
the floetz limestone, which occurs in the vicinity, and which also 
dips to the north 30°, as may be seen on the road toward Hazle- 
hatch. 
§ 136. Blocks and debris of the red sandstone conglomerate 
are to be observed scattered about this district. In the river 
Dodder, at the outlet from Glenismaule, is a block of this rock, 
seven feet long, by six feet broad and deep. Smaller detached por- 
tions are found also in the valley of the Dodder, and on the brows 
of the adjacent hills, and generally in the course of that river. 
They are strewed over the Tallow hills, and the Rathcool chain of 
hills, both on the higher grounds and on the flanks, and may be 
occasionally observed to the southward as far as the clay slate and 
greywacke country extends, on the western side of the granite 
region. I have incidentally also met with smaller fragments of the 
same rock on the eastern side of this mountain district, in the line 
of the Glencree, Gienculien, and Dargle rivers, on the banks and 
some way up the declivities of the adjoining mountains ; but no 
farther in the interior on the eastern side, until we approach the 
southern part of the county of Wexford* 
