16 On the Origin of “The Scalp.” 
afterwards unmasked, and redeveloped, by the stripping off of 
these strata during the Mesozoic period. At a much later period 
they were partially submerged under the waters of the glacial 
sea, but never again buried under more recent strata; as there is 
no reason for supposing that the Mesozoic formations were 
spread over this part of Ireland. 
It may be asked, however, “ Why have you assumed that the 
original river flowed from the north through the gorge of ‘The 
Scalp,’ rather than from the south?” This would be a very 
natural question, and one the reply to which is not very obvious. 
Still, whatever evidence exists is in favour of the view here indi- 
cated, namely, that the original stream flowed from the north. 
It will be observed that the little stream which now rises just to 
the north of “The Scalp” itself flows southward through this 
channel, and consequently that the slope of the bed of the ravine 
is in a southerly direction. This, I submit, affords a clue to the 
original direction of the old river; because it is extremely im- 
probable that the slope of the original river-bed would become 
reversed from any cause. All the chances are in favour of the 
original slope being retained; and 1 have therefore adopted the 
evidence afforded by the direction of the existing slope as that 
upon which to found an opinion regarding the direction in which 
the original stream may be considered to have flowed. 
On the lowering of the ground to the north of “The Scalp” to a 
level below that of this old river-bed, the stream would naturally 
take a course along the northern flank of the Shankill ridge, 
eastwards towards the sea; and as successive beds of the Carboni- 
ferous formation were stript off, the stream would work its way 
more and more northward, until ultimately it has attained the 
position of the Shanganagh brook of the present day. 
Before concluding it is right that I should state that a former 
President of the Geological Society of Dublin, Dr. Scouler,* has 
given it as his opinion that “The Scalp ” was formed subsequently 
to the Drift, or Glacial Period, on the ground that no vestiges of 
drift deposits are to be found in the valley of “The Scalp ” itself’; 
but even if it were the case, that no drift beds are to be found in 
the valley, it by no means follows that “The Scalp” was hollowed 
* Anniversary Address. Jour. Geol. Soc., Dub., Vol. I. 
