66* DOMAIN III. ARGILLACEOUS. 



European. To the European may be added, 



Micaceous clay slate, from Mont Blanc. 



Clay slate, mingled with chlorite, from Mont 

 Blanc. 



Purple clay slate, with spots of quartz and 

 mica, and thin layers of talcous schistus, from the 

 same. 



Soft grey clay slate, from the same. 



Grey clay slate, sometimes spotted with decom- 

 posed pyrites, from the summit of Snowdon, 

 where it rests in beds nearly horizontal, on arrects 

 or uprights of schistose keralite. 



A remarkable clay slate, of a yellowish brown, 

 with long streaks, so as to have the appearance of 

 oak board, with some knots of a deeper brown, 

 and others white. It is mingled with a little 

 quartz and mica. Sauss. 1482. 



STRUCTURE II. SECONDARY. 



This either occurs uniform, or with impressions 

 of vegetables, or sometimes of shells. 



Aspect 1. Uniform. Thick slaty shale, from 

 Derbyshire. 



Shale, from numerous coal-mines. 

 Variety. Bituminous shale, from the same. 



