INTKODUCTORY ESSAY. 



ranean channels^ and from this cause, together 

 with the breaking away of the face of the ridges, 

 has arisen the precipitous mural chlfs, so common 

 on the coast, and in the interior of the calcareous 

 or coralline district. 



The hilly portion, or that part of the island which 

 has been denominated Scotland^ and Below the Cliff'^ 

 is principally composed of mineral substances 

 belonging to the clay genus; particularly loam, 

 potter's clay, and slate clay. There is also found 

 here a fine-grained friable brown sandstone, which 

 is for the most part micaceous; and beds of very 

 loosely cohering black sandstone: also Gypsum, in 

 fragments, crystals, and distinct concretions, from 

 a very small size to such as weigh several ounces, 

 disseminated through beds of sandy clay : and there 

 occur, imbedded in the same, or scattered on the 

 surface, fragments of ferruginous conglomerate, and 

 of quartzy sandstone, and balls of flint and iron 

 flint: also a variety of other ores of iron, such as clay 

 ironstone, compact black ironstone, compact and 

 ochery brown ironstone, and the like. I have here 

 seen in a hill, from the white appearance of its 

 broken cliffs, termed Chalkey Mount, a bed of 

 porphyritic slate, or clinkstone porphyry, about 

 eighteen inches in thickness, lying between beds 

 of very loosely cohering sandstone, and dipping to 

 the N.E. at an angle of 30": also a bed, a few 

 inches thick, composed of alternate ]amin<e of 



