372 Account of the IVIiyfin Dykes in the ' 



pearance of crack or disruption, the strata on both side* 

 of the depression are all consolidated into one mass. 



When searching for whynn dykes upon our northern 

 coast, I was obliged to omii about four miles of it lying 

 between Beng(ire-Head and Carrickarede, as bcingf too 

 distaiU from Porlrush and Ballycastle, where I was used to 

 take boat, and totally void of shelter, even for the smallest 

 craii. 



To the westward of Ballycastle I saw only one dyke. 

 On the east side of Kcnbaan Point, a rock emerges from 

 the water, which I have no doubt is part of a dyke, from 

 the appearance it made ; and as I approached it, I perceived 

 it was formed of horizontal prisms : here too a ncv.- feature 

 occurred, common indeed in the dykes further eastward, 

 but which f had not observed in any of those I had yet 

 examined: the centre and sides of this one were con- 

 structed differently, the prisms in the centre being larger 

 than those in the sides, and all very neat, the grain too 

 probably, as in other cases, also differed ; but I was pre- 

 cluded from examining any «)f the circun)stances which 

 attended this cuiious little solitary rock, by the violent surf 

 which then broke upon it. 



Hitherto the precipice cut through by the whynn dykes, 

 and the rocks from among which they sometimes emerge, 

 were all basalt, uniformly stratified ; but the accumulation 

 of these strata, after regularly dipping, immerges beneath 

 the sea to the westward of Ballycastle, and a new system 

 of materials arises at the end of the strand to the eastward, 

 to wit, alternate strata of freestone and coal ; these are cut 

 through exactly in the same manner the basalt strata were, 

 bv vertical whynn dykes, which all run into the sea, across 

 the l)t.ach at the foot of the precipice. 



The first of these is about tw'O iliilcs from Ballycastle, 

 and though a rude imperfect one, it is not to be overlooked ; 

 the black or dark blue of the basalt being strongly con- 

 trasted with the brown colour of the freestone it passes 

 through on the beach j here the high road runs close un- 

 der the precipice, and affords a gt)od opportunity to ex- 

 amine the contacts of the basalt dyke with the freestone it 

 cuts through. 



'i he next dyke, some hundred yards further east, is more 



useful than an exammation of the intestine position of strata and veins: — in 

 short, ui>ou' this is louaded aH our knowledge of ;^oIugy ; it is, however, 

 rtUendcuTviili jfieat lal>our and di?u:aiiy/' ^Jameson's Mineralogy, of Scot- 

 Lad and Arrau, [jaj^e -. - " ':::amiaatiou isattciidcd ncith'.r 

 witK Lboui- :*Ji- difiicU' 



per feet J 



