IV. On the Dykes of the North of Ireland
M.D. Member of the Geological Society.
Road November 4th, 1814.
My object in the following paper is to describe some of the
more general characters of Dykes, such as I have lately observed
them in the North of Ireland.
I do not know exactly within what geographical limits these curious geological phenomena are to be met with: they are common on the Western coast and in the Isles of Scotland, and I have observed them also in the Isle of Man. I understand that none have yet been remarked in the South of Ireland, and I did not observe any in the Midland counties through which I passed between Dublin and the Northern coast. In England they have been found in the centre of the island, as at the colliery of Tividale in Staffordshire; but in the North of Ireland it is only on the verge of the coast that they abound, and it is there that I have principally examined them. Of more than sixty that I noticed, nearly half were situated on the shore; those which occur in the mountains of Donegal are I believe the remotest from the sea, and those lie within fifteen miles of it.
I have not found their occurrence to depend upon the absolute elevation of the country in which they appear. I have observed them at almost every altitude between that of the shore and those which I have inserted in the following Table, as being the greatest and somewhat uncommon.
