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trap, at Boneyclassagh, half a mile east of Dunluce Castle, on the south 

 side of the road. The columns are quarried, to be broken for the roads, 

 being more easily got. The breeciated trap is softer and tougher, and 

 is not so good as a road material, and is more difficult to quarcy. The 

 columns are about 6 feet long and 6 to 8 inches diameter. The whole 

 columnar mass is like the upper arms of a fork; and though a junction 

 was not exposed when I was there (August, 1858), I believe they join a 

 few feet down. The right branch of the fork is composed of two 

 separate dykes ; the left only one. The columnar trap here appears to 

 have been projected into the breccia, and to terminate in a rough, 

 lenticular form. There is no ochre adjoining it, which would afford a 

 facility for opening a crevice, when the rock was agitated. There 

 must have been a violent rupture in the tough breccia. I suppose the 

 two arms of this dyke to join below in the form of the letter Y. 



Fig. 8. 



"Whin Dyke in breeciated Trap, at Boneyclassagh, near Dunluce. 



There is a peculiarly- shaped mass of trap at Ardihannon, on the 

 east side of the little road that leads from the hotel down to the Giant's 

 Causeway. The whole mass is intruded into the great layer of brec- 

 cia near the top of the cliff at the Causeway. The mass affects the 

 columnar form ; but it is not columnar ; it is more in the form of solid 

 flag-like sheets, from six to twelve inches thick. The joints are smooth 

 but uneven and irregular. At the right-hand side, looking up, it ap- 

 pears to be columnar. Towards the middle, the masses are bent, so 

 that the two ends form an angle at the bend. This is the rudest of the 

 masses, with any pretensions to articulation, which I have seen on the 

 north coast. This trap, like all the other columnar trap, is very fine- 

 grained, so as to give a conchoidal fracture, similarly to that in the 

 columns at the Causeway. The place has the appearance of an attempt 

 having been made by adventurous labourers to quarry some of the 



