MICACEOUS SCHIST. 



exist. These are of igneous origin, as will be per- 

 ceived by turning to the nineteenth Chapter ; and, as 

 formerly suggested, we must here consider, that after 

 the deposition of these strata, they were subjected to 

 that degree of heat which permitted the minerals to 

 crystallize ; as they do, in similar circumstances, in 

 the volcanic rocks. 



As the composition and texture of micaceous schist 

 are infinitely various, no general statement will in- 

 clude the different effects which follow its decomposi- 

 tion. Hence the varying appearance of the moun- 

 tains which occupy the great belt that reaches from 

 the Mull of Can tyre to near Stonehaven ; and thence 

 the characters of the soils are equally various. In 

 some places it is a deep and fertile yellow clay, from 

 the prevalence of mica in the rock, while, in others, 

 when the proportion of quartz is large, a barren and 

 thin sandy covering separates the brown peat from 

 the solid rock. 



Its (Economical uses are very limited, from the irre- 

 gular nature of its fracture, though the tender vari- 

 eties are sufficiently tractable for use; while, it is often 

 a substitute for slate, well calculated to resist the 

 winds of a boisterous region. A sculptor might be 

 surprised to see it applied to his own art; yet the 

 cross of Campbelltown and those of lona, ornamented 

 with Runic knots and foliages, present an intricacy of 

 design exceeded only by the precision and durability 

 of the workmanship. If it is esteemed, on the con- 

 tinent of Europe, as a material for lining furnaces, 

 that can only be true of those varieties which contain 

 a large proportion of quartz ; as it is fusible in a very 

 moderate heat, where the mica abounds. Metalliferous 

 veins occur in micaceous schist ; containing iron, ar- 

 senic, lead, zinc, cobalt, and, rarely, gold. The mine 



M 2 



