§ 1. On the Geological Feature: of the North of Ireland.
The arrangement adopted in the following observations is, that suggested by the geological position and relations of the rocks described.
| I. Primitive Rocks | A. Granite. | |
| B. Gneiss and mica slate. | ||
| C. Primitive limestone. | ||
| D. Primitive trap. | ||
| E. Porphyry | ||
| F. Syenite |
A. Granite.
In the Mourne mountains and adjoining districts an extensive formation of granite occurs, but neither here nor elsewhere in the north of Ireland can we recognize the same varieties of that rock which the mountains of Wicklow present.
The granite now to be described seems rather to agree in its characters with the newer granite of the Wernerians, a rock supposed to be closely allied to syenite. It appears to constitute almost the whole mass of the Mourne mountains, whence it passes across Carlingford-bay into the county of Louth, extending to the summit of the Ravensdale mountains. It soon crosses the limits of Louth to enter into Armagh, composing part of the Faughel hills, whence it expands itself into a flat and elongated ridge, well known under the name of Slieve Gullen, forming likewise the Slieve Girkin or Newry mountains, and the lower and upper Fathom hills, of which the latter keep close to the right bank of the Newry river.
On the north-west side of the Mourne mountains, where they
