303 



shore under high water mark, half-a-mile south-east of Culdaff House, 

 in Donegal. This kind is sometimes called onion basalt. 



5. Greenstone is a granular rock, composed principal^ of two sub- 

 stances — felspar and hornblende. The felspar is imperfectly crystallized 

 and is more abundant in this rock than in basalt. Greenstone is rather 

 a scarce rock in Antrim. It occurs at Fair Head in a great overflow, 

 which covers that promontory. This overflow appears in enormous 

 vertical prismatic masses, often quadrilateral, which are destitute of the 

 regular articulation and neatness of form which distinguish the basaltic 

 pillars of the Causeway. A single rude column is seen standing at 

 the Gray Man's Path. It appears to be formed of a bundle of 

 smaller ones which decompose into similar masses of unequal sizes. The 

 greatest height of the precipice is 317 feet, and nearly perpendicular. 

 The concretions of this greenstone are distinct and large. It also con- 

 tains augite. 



Slievemish, or Sleamish, is composed entirely of greenstone. It is 

 seven miles east of Ballymena ; it is 1437 feet high ; the sides are steep, 

 and it forms a gigantic landmark in the country, and can be seen for 

 many miles to the north, west, and south of Lough Neagh. It is longer 

 in a north and south direction than from east to west. The greenstone 

 of this mountain is fine-grained, and the crystallization more perfect than 

 usual. The felspar is of a brownish red colour. 



The hill of Tieveara, half a mile west of Cushendall, is an eruption 

 of greenstone. It is in form of a truncated cone, very steep at the sides, 

 and roundish on the top. The greenstone is highly crystalline, the 

 crystals large, and the rock rather porous, so that it admits water, and 

 easily falls away by decomposition. 



Red Ochre or Boles. — This is a soft rock. It occurs on the north coast 

 of Antrim in layers from three inches to two or three feet in thickness, 

 between the tabular masses of trap about Bengore Head and the Cause- 

 way (Pis. XXIY. and XXV.). Some of the red layers are from 10 to 15 

 feet thick or more. On the north-east face of Trostan mountain, 

 three miles south west of Cushendall, a layer is 30 feet thick and 

 half a mile long or more. Many layers of it are interstratified with 

 the black layers of hard and soft trap at Garron Point (Pig. 4). 

 About 10 chains south of the Bull's Eye Waterfall, near Glenarm, 

 there is a perpendicular cliff of it on the river side about 40 feet 

 high. Some of the layers in this cliff' are hard, some red, and 

 some a lilac colour, so soft and soapjr that they could be easily cut 

 with a knife like a piece of soft chalk ; the layers are from two 

 to four feet thick, and in some are imbedded clear quartz crystals the 

 size of grains of partridge shot, with double pyramids complete. 



7. Tabular Trap. — This rock is well developed at Bengore Head, on 

 the north coast (PL XXIV., beds Nos. 1, 2, 3). It is there spread out 

 in black layers, nearly horizontal, from 5 to 1 5 feet in thickness, and 

 from a furlong to a mile in length. The black layers (Nos. 4, 5, 6) are 

 separated from each other by thinner layers of red ochre, from three 

 inches in thickness to three feet; sometimes much more. This bole or 



