Page:Transactions of the Geological Society, 1st series, vol. 3.djvu/204



Descriptive Notes referring to the Outline of Sections Presented by part of the coasts of Antrim and Derry,

Collected by the Rev., M.G.S.

From the joint Observations of

The Rev, M.G.S. Reader in Mineralogy to the University of Oxford,

And himself, during a Tour in the Summer of 1813.

The Section, Plates 10. 10*. accompanying these notes, exhibits a line of coast extending rather more than fifty miles from the promontory on the south of Glenarm The first point in which the cliffs of the Antrim coast expose sections of the basaltic rocks, is Blackhead, on the south-east of the peninsula of Magee; this point is (following the indented line of the coast) more than twenty miles to the south of that at which the delineations accompanying this paper commence: our information concerning that interval not being sufficiently precise to admit its being exhibited in such a form.

The following short notice will however contribute in some measure to supply the deficiency, and being prefixed to the descriptions in the text will render them a continuous survey of all that part of the basaltic area which presents a precipitous face towards the sea.

From Blackhead the eastern coast of the peninsula of Magee exhibits a long and lofty range of basaltic cliffs called the Gobbins, extending nearly eight miles towards Portmuck at the north-east extremity of the peninsula; near this point the chalk emerges from beneath the basalt, and the lias from beneath the chalk. Hence to the mouth of Lame tough the cliffs cease, the hills rising with a gradual acclivity from the beach; the same character is applicable to the opposite side of the lough near Larne: the chalk and lias, continue to occupy the level of the sea through this space, but about two miles to the north of Lame the chalk again sinks beneath the low basaltic cliff of Black-cave-head; a ridge of the same rock extends from hence skirting the beach for three miles to Ballygelly head, a promontory exhibiting rude and irregular columns; near this point the inferior strata emerge, but from the flatness of the coast being flat do not render themselves distinctly visible. About three miles beyond Ballygelly-head however the red mule (No. 4 of the Introduction) may be traced, and about two miles further the lias begins to show itself in the southern extremity of the Deer park hill of Glenarm: this is the point at which the engraved section commences. in Antrim, to the strand of Macgilligan in Londonderry, where the basaltic mountains receding to the south finally quit the vicinity of the sea.