126 
Mr. Weaver on the 
Ovoca, from the same > 
point to Arklow, is . . J * 
Feet 
292 
Hence it also appears, 
that the bottom of Glen- 
malur stands higher than 
the level of the lake in 
Glendalough 273* 
being per mile on a line of 
. 42 feet . . . 7 miles 
§ 8. The Southern and Western chains, (see PI. 7. No. 3, 4, 5, 
and 6,) partake both of the primary and secondary character, con- 
sisting principally of clayslate supporting sandstone ; but the Cen- 
tral group is of more recent production, being composed of coal 
tracts, which repose immediately on floetz limestone ; (see PI. 6. 
No. 2.) Of the former, I have no ascertained heights, but by 
comparison with the given elevations of other mountains, a prac- 
tised eye may obtain a general idea of their elevation ; and it ap- 
pears to me that their highest points are not more than between 
2000 and 2500 feet above the sea. The elevation of the Central 
group above the limestone plain, may be seen in the two accom- 
panying sections, (PI. 14. No. 1 and 4). The highest points are 
about 1000 feet above the level of the sea. 
§ 9. The Northern boundary of our field forms a portion of 
that hilly tract, which rising on the south-west in the county of 
Longford, extends east to the bay of Drogheda, and in a north-east 
* Glenmalur stands probably upon nearly the same level as the Glen of Imale on the 
western side of the central chain ; for although the Slaney under Tuckmill bridge be only 
397 feet above low water-mark, it is to be considered that the river has travelled a distance 
of seven miles from the Glen of Imale to this spot. 
The Barrow at Carlow is only 162 feet above low water-mark ; and therefore 235 feet 
below the Slaney under Tuckmill bridge. 
These observations tend to shew, that the general surface is lower on the western than 
on the eastern side of the central part of the eastern chain ; and that the ge'neral declivity 
on the western face of this mountain chain, is more rapid than on the eastern. 
