306 



of an old crater, the appearances about Bengore Head convey the same 

 idea in a still more striking manner. Looking from the sea at the land, 

 it is like the ruins of the internal part of one side of a crater. The se- 

 veral successive layers erupted, and spread out, one over another, are 

 there, clear and visible, and leave no doubt of the existence of a former 

 volcano. Considering, then, that the crater of an ancient volcano exists 

 in the present ocean — say a quarter of a mile north of Fair Head, and a 

 similar crater a quarter of a mile north of Bengore Head — considering 

 also the abrupt, precipitous character of the northern coast, from Fair 

 Head, through the coal-measures at Ballycastle, by the headlands about 

 Bengore Head, and on to Magilligan, in Derry — the conclusion is ine- 

 vitable that a fault exists along, near the north coast, probably through 

 the centres of the two craters, from Fair Head by Bengore Head and 

 Magilligan, into Lough Foyle. All the rock to the north of this line 

 has gone down, or the dry land to the south of it has been heaved up. 



At Bengore Head, the highest part of the land in the immediate vici- 

 nity is at the top of the cliffs on the coast. From that the surface, 

 which is the top of the upper columnar layer of trap, slopes back south- 

 wards for some furlongs, as it does at Fair Head. All the layers have 

 a southern dip, and the stratified rocks on this part of the coast, that is 

 the coal-measures, the lias, and the chalk, where they appear above the 

 level of the water, have all a southern dip also, at a low angle, gene- 

 rally from 5° to 10°. Those latter rocks do not appear to be much dis- 

 turbed since they were first deposited ; the beds or the layers do not 

 appear anywhere upset on their edges, as they do in the older rocks. 

 The trap layers especially are near to the angle at which they were ori- 

 ginally spread out, and the rise to the north seaward along the coast 

 appears to confirm the idea that there was higher land to the north than 

 we now see at the time of the eruptions which compose the present 

 layers of the shore, and that the upper layers of liquid lava flowed from 

 their sources to the south in this locality. 



This section at Bengore Head, however, is not typical of sections in 

 the county generally. The section (Fig. 4) at Garron Point, which is 

 also well exposed, consists of a much greater number of layers, and 

 those much thinner, the thickest of them seldom exceeding eight or ten 

 feet, and more generally from three to six feet. There are no columnar 

 layers, and no thick layers of tabular trap ; there are a few of red or 

 brownish-red ochre, the rest are all hard and soft dark-coloured layers, 

 often alternating. Indeed it may be said of the trap sections of Antrim 

 that there are no two of them alike at five miles distance. 



The basalt ends at Port Braddan, in a vertical fault, where it joins 

 the chalk of Whitepark and Ballintoy ; this part of the coast further 

 showing that the chalk at Whitepark has been heaved up, or the rocks 

 about Bengore Head relatively let down. 



The section at Bengore Head suggests a few ideas for speculation 

 regarding the succession of the layers. It appears to me that the layers 

 of tabular trap that now lie immediately upon the chalk were the first 

 that were erupted and deposited in each locality, and, in a general way, 



