14 On the Origin of “The Scalp.” 
of the surface southwards, it .is easy to conceive that a stream 
might have commenced to run along a channel in the coal- 
measures, directly over the line now occupied by “The Scalp.” 
There would thus be a high sloping plane of Carboniferous strata 
lying to the north of the Dublin mountains, and forming 
gathering ground for a stream which took its course along the 
tract now occupied by “'The Scalp” towards the sea, very much 
in the direction where the river Vartry enters the sea at the pre- 
sent day. If we restore the original strata in the manner here 
indicated we shall find that the Carboniferous beds must have 
completely enveloped all the granitic region of a lesser elevation 
than Kippure, Lugnaquilla, and some of other high eminences ; 
even after making allowance for a considerable amount of de- 
nudation from off these eminences themselves. 
Fig. 1.—Geological section through the Central Plain, and Wicklow 
Mountains, restoring the original Stratification as at the close of the 
Carboniferous Period. 


















Paes ee a ~ . 
SECTION]. COAL MESA CLS URIR SES 
ee ————————————— r- 
——— = : a oS 
a a ee = =~, 
——— = = SSSR SEES 
fi 4 ii 4 1 " L ty 
x X x x ey SSAA SO BE 
wv * . % “x x tet fe, ee eS » “ ‘s x x x x x x SS SSE SRS ee 
Gi RoaAGeN | era if E SCHIST AND QUARTZITE 
I conclude, then, that a stream flowed southwards and eastwards, 
from a higher plain lying where the lower plain of county Dublin 
is at present, and passing over the ground now occupied by the 
Sealp,and the depression extending to the Vartry valley, eastwards 
towards. the sea, which was probably much further off than at 
present. The period through which the land was now exposed 
to denudation was immensely extended, ranging downwards 
through the Mesozoic into Tertiary times; and throughout this 
enormous lapse of time the central plain of Ireland was being 
denuded of its coal-formation, and, to a large extent also, of the 
Lower Carboniferous rocks which underwent chemical dissolution 
from waters charged with carbonic acid. During this time the 
whole country would be exposed to denudation—river channels 
would be formed in the Carboniferous beds, and (when these were 
removed) in the underlying granitic and schistose rocks. It was 
at this stage that I consider “The Scalp ” to have been cut out of 
the granitic and Silurian schists; and the question next arises— 
