Page:Transactions of the Geological Society, 1st series, vol. 3.djvu/231



IV. On the Dykes of the North of Ireland

By , M.D. Member of the Geological Society. Road November 4th, 1814.

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.