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On the shore, a little to the west of the pier at Ballycastle, a sin- 

 gular vein occurs in the chalk, which there forms the lower portion 

 of a cliff, capped with basalt. The basalt immediately over the chalk 

 approaches to the character of wacke. The vein in question is cal- 

 careous, but includes imbedded balls of wacke, to the presence of which 

 the difference of its characters from those of the chalk that it traverses 

 may, perhaps, be attributed. The limestone forming the vein is com- 

 pact, breaking spontaneously into parallelopipeds, the greater side of 

 which is perpendicular to the direction of the vein. The width of this 

 vein or dyke is 17 feet. It contains about nine- tenths of calcareous 

 matter, with some clay, and specks of bright mica. 



There are a few whin dykes in the coal-measures at Murlogh Bay ; 

 two at the upper end of Cloughlass glen, Station No. 22. A large pro- 

 trusion of columnar trap at Ballgalley Head, three miles north of 

 Larne, which tilts up the beds of chalk on the south side of it to a ver- 

 tical position. Another large dyke, or perhaps a continuation of the 

 Ballygalley protrusion, occurs at Ballygawn, two miles further W.W. 

 This dyke is 60 yards wide, cuts through the chalk, and alters it for 60 

 feet on each side, so that when struck with a hammer it falls into 

 sand. 



Carrickfergus castle stands on a large trap dyke. There are about 

 seventeen dykes between Carrickfergus and Belfast, on the western 

 shore of the Lough ; eight at C ultra on the south shore ; four or six at 

 Cave-hill, and Ballysillan ; five or six more at Allan's ravine and 

 Bally money (Fig. 2) ; eight at Aughnahough (Station No. 3, Fig. I) ; 

 and half a dozen at Banner's glen and Moira, already noticed at those 

 stations. I consider that describing these several dykes more in detail 

 would be tedious, and would lead to no useful result. 



Whin dykes, and the rocks they traverse, have not undergone any 

 modern disturbance beyond superficial abrasion, but they remain in the 

 same situation as at the remote period at which they were formed. 



Fig. 10 is a sectional sketch, to represent the position of the 

 rocks at Portrush, and at the Skerries Islands near it. These rocks, 

 about the year 1790, were the theme of much controversy between the 

 geological parties of that time. Fossils were found in a hard, black, 

 fine- grained rock here, which very much resembled some varieties of 

 trap ; and from this it was said the trap contained fossils by one party ; 

 this was as stoutly denied by the other. 



The masses d d, are greenstone dykes, which are parallel to the 

 bedding of the lias, and most probably are emanations from the Port- 

 rush mass, which by force from below were projected into the beds of 

 the lias, and came to the - surface at d d, immediately under a a, 

 beds of soft lias clay, which are usually full of the fossils of that rock. 



The lias clay at a a, where it is in contact with the green- 

 stone, instead of being a soft bluish-gray clayey rock, as it occurs 

 in ordinary cases, is converted into a very hard, black, close-grained 

 silicious rock, wholly different in lithological character from the ordi- 

 nary aspect it assumes. This change is supposed to have been effected 



