MOI>E II. CLAY SLATE. 



" It is a very widely-extended rock. In this 

 country it skirts the Highlands, from Lochlo- 

 mond, by Callender, Comrie, and Dunkeld ; in 

 the whole of that extensive district resting on, 

 and gradually passing into, mica slate : the same 

 appearances are to be observed in many other 

 quarters in Scotland. On the Continent of 

 Europe it has been traced through a great extent 

 of country : thus it occurs in Saxony, Bohemia, 

 Silesia, Franconia, Bavaria, the Alps of Swis- 

 serland, Austria, Hungary, and many other 

 parts in Europe. It occurs also in considerable 

 quantity in North America, as Pennsylvania ; 

 also in immense quantity in South America: 

 thus it is said that nearly the whole country 

 between Potosi and Lima is composed of it."* 



It is self-evident that a wide distinction should 

 be made between this important and universally 

 diffused substance, and the siderous slate which 

 is used in architecture. 



In his mineralogy, Mr. Kir wan seems to have 

 blended the primary and secondary argillaceous 

 schistus, when he mentions that it sometimes 

 bears impressions of vegetables and shells f; but 

 in his geological essays, which are valuable as 



* Geognosy, 125. 



f In the vale of Chamouni it is found impressed with am- 



monites. 



