Wricut— Glacial Drainage round Montpelier Hill, Co. Dublin. 577 
and the Glen of the Downs; the first cuts across both the granite 
axis and the strata of micaceous schist which recline against it ; 
the second is nearly parallel to the first, and the third has cut 
through strata of quartz-rock. All these ravines contain vast 
detached blocks of the adjacent rocks, granite in the first, and 
quartz in the second. Now it appears probable that the forma- 
tion of these ravines was subsequent to the deposition of the shelly 
gravels; for had they existed along with the valleys containing 
transported matter, it is difficult to conceive how they should now 
be so thoroughly destitute of all vestiges of it, especially when it 
is remembered, ‘that none of these ravines ever possessed any 
stream which could carry off their contents. As many of the 
shelly gravels occupy a higher level than these valleys, it is incon- 
ceivable if both orders of valleys were contemporary, and both 
equally under the water, as must have been the case, upon what 
principle of selection one set were the receptacles of transported 
matter while the others escaped? It therefore appears probable 
that the ravines were of later origin and are with the shattered 
blocks which are still in situ, the indications of the nature of that 
force which has elevated the shelly beds into their actual position.’” 
The Rev. Maxwell Close’ also drew attention to these curious 
valleys, and recognized that they were directly connected with the 
other glacial phenomena of the district, suggesting that they 
might have been formed by the excavating action of ice. He 
remarked on “the straightness and better definition of those 
valleys on the east side of the mountain range; the fact that their 
cols are often situated to the west of what seems to have been 
the original position of the watersheds of the passes: the last two 
peculiarities are precisely what might be induced by a glacial 
flood of sufficient denuding efficacy, coming from the north-west, 
partly dammed up by the long mountain barrier, and pouring over 
the crest thereof down the steeper slope of its lee-side.”’ 
The transverse gully, which is the most striking feature in the 
small area here described, trenches completely across the lowest 
1 «* Account of Certain Elevated Hills of Gravel, containing Marine Shells, which 
occur in the County of Dublin,’’ by John Scouler, Journ. Geol. Soc., Dublin, vol. i., 
p. 266. 
2 Rey. Maxwell H. Close, ‘‘ Notes on the General Glaciation of the Rocks in the 
Neighbourhood of Dublin,’? Journ. Roy. Geol. Soc. of Ireland, vol. i., p. 3, 1864. 
