Page:Transactions of the Geological Society, 1st series, vol. 3.djvu/158

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The colour of this sandstone is reddish or greyish; its texture is either conglomerate, including fragments of greywacke slate, or finely granular, composed of quartzose grains imbedded in a cement, sometimes calcareous and sometimes siliceous. The greenstone which caps this hill differs very slightly from that associated with the floetz trap.

Lord Londonderry has caused this formation to be bored to the depth of 500 feet in the fruitless search for coal on the east side of Strangford lough near Mount Stewart; if to this depth the height of the sandstone on Scabro hill be added, it will give from 800 to 900 feet as the known thickness of this formation. The greatest length of this district of sandstone does not exceed six or seven English miles. it appears to rest upon greywacke.[1]

The tract of this formation between the bays of Cushendall and Cushendon, is yet more limited than the preceding. On the coast it occupies a line of between three and four English miles, and extends about the same distance in an inland direction. The highest point of the cliffs on the coast in this range is only 124 feet; but the hill of which they form the escarpment rises at Jeaveragh near Cushendall church to the height of 522 feet: this is the greatest elevation which the sandstone of this district attains.

The strata dip into the sea towards the E.S.E. under an angle of about 32°. In the bay of Cushendon several caverns of considerable magnitude occur in this rock.

The general character of this formation is that of a conglomerate; it passes however into a coarsely granular texture, and in one place (the Red bay of Cushendall) into a finely granular: its colours vary from red to grey.

  1. The arrangement of the sandstone formations in the north-east counties of Ireland, forms the most difficult problem presented by their geological relations. The sandstone of Lough Strangford with its cap of greenstone presents so obvious an analogy to the structure of Cragnashoack at the southern extremity of the floetz trap chain in Londonderry, that we might be almost tempted to infer the identity of the sandstone in both instances, and, since that of Cragnashoack is certainly the newer variety, to question the propriety of assigning to that of Scabro hill the antiquity which has been claimed for it in the text: its apparent connection with the sandstone of Belfast lough, also seems to favor the idea of its belonging to the newer variety, for in travelling between Belfast and Newtown Ards, the road is said not to exhibit any rock but sandstone, in situ, although hills of greywacke rise within a small distance on either side: yet the fact mentioned by Dr. Berger of the alternation of this sandstone with greywacke, seems decisive as to its age.

    The sandstone of Cushendon also appears to require further examination: one of the, most interesting facts concerning it appears to have escaped Dr. Berger's notice, namely, its connection with a formation of reddish clay porphyry. The observations made by Mr. Buckland and myself on this formation will be found in the account of the sections presented by the coast, appended to these extracts. It is only mentioned at present as affording an analogy between the sandstone which skirts the mica slate of Cushleak, and occurs in a similar situation in the island of Arran.