4io On the ROCKS in the 



ry capable of embracing all the phenomena, which the con- 

 struction of his fyftematic arrangement led him to obferve. A 

 peculiar language was therefore indifpenfable ; and as this 

 language has been conftructed with fo much regard to his theo- 

 ry, unlefs that is underftood and adopted, his terms become ufe- 

 lefs. 



By a formation is meant, any feries or fuite of rocks which 

 ufually occur together j hence the Coal Formation is compo- 

 fed of 



i. Sandftone, 6. Limeftone, 



2. Coarfe Conglomerate, 7. Marl, 



3. Slate-clay, 8. Clay-ironftone, 



4. Bituminous Shale, 9. Porphyritic Stone, 



5. Indurated Clay, 10. Greenflone *, 



with which the Coal occurs in numerous beds, varying extreme- 

 ly in thicknefs. Thefe, however, never all occur together, and 

 it is no detriment to the Coal Formation fuite, even if Coal it- 

 felf mould not be found among them. 



Again, the term Flcetz is given to all the formations, contain- 

 ed between the tranfition and alluvial rocks, and implies that 

 they are diftinguifhed by their frequent occurrence in beds, 

 which are much more nearly horizontal, than the primitive and 



tranfition 



* Greenflone is a literal tranflation from the German ; it is an extremely im- 

 proper name ; but as we have no other by which we can distinguish this variety 

 of trap, we muft ufe it till a more appropriate is found, even at the expence of 

 fuch language as red and blue greenjiones. In the mean time, it muft be under- 

 ftood merely as an arbitrary term. 



