157 



CHAP. XXVII. 



Micaceous Schist. Chlorite Schist. Talcose Schist. 



THOUGH I have placed Micaceous schist next to gneiss, 

 in conformity to the general opinions respecting its 

 order in nature, it has already appeared, and will soon 

 he still more evident, that this order is not constant. 

 If a definition of so familiar a rock is nearly super- 

 fluous, it is needful to say, that it ranges between mica 

 and quartz, so that as the examples on one side consist 

 of little else than condensed mica, the others pass into 

 quartz rock by an imperceptible gradation; as is com- 

 mon especially at the mutual boundaries of these two 

 deposits. The varieties must be sought in the Clas- 

 sification of Rocks ; yet I must note here, as essential 

 to its theory, that it occasionally contains fragments, 

 or portions of a conglomerate. 



In this island, micaceous schist is limited to moun- 

 tainous districts; the features which it confers on the 

 country being various, and often picturesque. In 

 some tracts, the hills are tame and undulating, like 

 those of argillaceous schist; ranging from 500 to 1000 

 feet in height, and rarely broken by projecting rocks, 

 whence they gradually rise to upwards of 4000 as in 

 Ben Lawers; acquiring more striking characters, and 

 displaying abrupt precipices, with summits occasion- 

 ally serrated, arid partially covered with vegetation. 

 As this rock often presents considerable fissures, and, 

 while mouldering more readily than gneiss, is favour- 

 able to vegetation, the lower cliffs and precipices are 

 often covered with trees, producing a variety of pic- 

 turesque scenery well known in the vicinity of Loch 

 Cateran. In Scotland, as elsewhere, it occupies ex- 

 tensive tracts, unmixed with any other rock, but oc- 



