EXCURSION XVI. 



197 



features are well shewn in the cut annexed (fig. 36), which 

 represents the cliffs at Kingscove, with Drumadoon Point 

 in the distance. 



The porphyry of the cliff is in columnar forms, the 

 pentagon being the prevailing figure, and there are irregular 

 flat jointings; the pillars are from 1 to 2 feet in the side, 

 and the height 80 or 100 feet at the middle or highest part 

 of the precipice; the entire height being about 230 feet. 

 The porphyry has a base of compact felspar or clinkstone of 

 a whitish or brownish gray or dark-blue colour, and im- 

 bedded crystals of glassy felspar or pearlstone, common 



Fig. 36. 



felspar, or earthy felspar, in a state of decomposition, and 

 with an unctuous feel, like steatite ; there are also transparent 

 bits of quartz, easily known from felspar by not shewing any 

 laminated structure, with the form and lustre of crystals 

 whose angles have been worn off; the base is often dark and 

 has cavities lined with black oxide of iron. The rock is 

 thus a quartziferous felspar porphyry, often ironshot. The 



