The pillars are composed of the most compact and homogeneous variety of basalt, containing a small quantity of steatite occasionally imbedded in its mass, and possessing the property of being more or less sonorous when struck by the hammer.
Besides the well known columnar strata exhibited by the Giant's Causeway and adjoining cliffs, of which the principal is 54 feet in thickness, and a second 44 feet, similar strata are exhibited in the following places.
In Glen Ravel, at the distance of about four miles from Cushendall, I observed in the bed of a stream flowing from the mountain of Slieveance, an abrupt façade of tabular basalt, approaching the columnar form, fronting the north-east quarter.
In the isle of Rathlin, there are several systems of pillars along I the northern coast: at Kenrammer, “ the thick Head,” I counted no less than seven in succession all nearly vertical, but none very I regular; some were matted amongst themselves.
At Thivigh, “ the side-point,” there is a sort of headland sloping down into the sea; it is covered with grass, but the section sideways exhibits two assemblages of square pillars, not unlike those of Fair-head; the lower system comprehends those of the greatest dimensions; the upper one, those that are the best defined.
Rhue-na-Scarse or Roanscarave, in the town-land of Craigmacagan, presents another projecting point of land, with a real causeway, in neatness hardly inferior to the Giant's causeway itself, the pillars being almost vertical; the pavement is nearly flat or horizontal.
At Doon-point, tabular basalt alone occurs; whence it appears that the late Dr. Hamilton has mistaken it either for Thivigh or Rhua-na-Scarse.
Near Ushet-haven, on the south-east side of a hill, named in Irish Broagh-mor-na-Hoosid, there is another very elegant causeway: