410 On the ROCKS in the 
ry capable of embracing all the phenomena, which the con- 
ftruction 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 ; hence the Coal Formation is compo- 
fed of 
1. Sandftone, - 6. Limeftone, 
2. Coarfe Conglomerate, 7. Marl, 
3. Slate-clay, 8. Clay-ironftone, 
4. Bituminous Shale, = —‘g._-Porphyritic Stone, 
5. Indurated Clay, 10. Greenftone *, 
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 fhould not be found among them. 
Acatn, the term Fletz 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 
* Greenftone 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 greenftones, In the mean time, it muft be under- 
ftood merely as an arbitrary term. 
