186 Dr. Berger o« the Geological Features 



4. Grey stone. 



The top of Squires hill and of Cave hill, near Belfast, are both 

 composed of this rock. 



5. Clinkstone Porphyry. 



The little table-land forming the summit of Divis mountain con- 

 sists of a beautiful clinkstone porphyry of a reddish brown colour, 

 Containing elongated lamellar crystals of glassy felspar, and concre- 

 tions of bluish white chalcedony : the rock is very sonorous. A 

 variety of clinkstone porphyry also occurs in the neighbourhood of 

 the old red sandstone, near Newton Glens, so situated that it is 

 difficult to pronounce what is its position or geognostic relations 

 with regard to that rock : it will be more particularly described in 

 the explanatory notes on the section. 



The porphyries of Sandy-brae, &c. in the interior of the basaltic 

 arae, of which the geognostic situation is likewise uncertain, are 

 referred to a separate article at the end of these extracts. 



6. Bole or Ochre 



Occurs in beds of various thickness, alternating with and under- 

 lying the basaltic strata in the cliffs near the Giant's Causeway j 

 in Cave hill, on Macgilligan, along the east side of Ushet lough 

 in the isle of Rathlin, and in several other places. Although the 

 specific gravity of the bole is low it contains a great proportion of 

 iron, (acting powerfully on the magnet) and might with propriety 

 be classed among the earthy and ochrey ironstones. 



