Page:Transactions of the Geological Society, 1st series, vol. 3.djvu/130



The Mourne Mountains form a well defined group extending from Dundrum bay to Carlingford bay in the southern extremity of Down.

Slieve Donard is the highest summit of this group; it has been said to rise 3150 feet above the level of the sea, but the estimate of Mr. Templeton, who assigns only 2590 as the elevation of the highest points of the Mourne Mountains, appears more correct, and nearly agrees with that of Dr. Berger, who calculates its height at 2654 feet.

To the west of the main group the Fathom hills, Slieve Girkin or the Newry Mountains, and Slieve Gullen, all situated in the south-east of Armagh, and the Ravensdale and Carlingford Mountains in the north of Lowth, may be considered as its appendages.

Granite is the prevailing constituent of all these ranges.

To the north of the Mourne Mountains Slieve Croob composed of syenite, and Slieve Anisky of hornblende rock, both situated in the county of Down and barony of Lower Iveagh, constitute an elevated tract dependent upon but placed at some distance from the main group.

Hornblende rock and primitive greenstone are abundant on the skirts of the granitic district. Mica slate has been noticed only in one instance. Exterior chains of transition rocks advance far to the west and north of this primitive tract, extending westwards across Monaghan into Cavan and on the north-east to the southern cape of Belfast Lough and the peninsula of Ardes.

The primitive nucleus bears but a very small proportion in superficial extent to these exterior chains, which are principally occupied by greywacke and greywacke slate.