COAL STRATA. 
Ill 
in whose infancy and youth both these 
positions were subjects of frequent contro¬ 
versy by learned men. 
In order to unravel the story of the coal 
deposits^ we must advert to the associated 
rocks; the subject, like a contested passage 
in an ancient author, requires the aid of the 
context to render it intelligible. 
The dark hard mountain limestone, or 
some inferior rock, supports a series of nu¬ 
merous beds of sandstone and clay inter- 
stratified with layers of coal. 
The sandstones are the consolidated frag¬ 
ments of other previously existing rocks; 
the clays and shales are finer accumulations 
of similar materials ; the whole evidencing 
a mechanical deposit from water. The 
contained layers of carbonaceous matter 
are mineralized in their structure, and were 
long supposed to be of mineral origin, but 
the frequent occurrence of fossil vegetables 
in various states of preservation, and the 
investigations both of botanical and chem¬ 
ical observers, have rendered their vegetable 
derivation an unquestionable conclusion. 
fhe distinct plants found in the coal are, 
