455 
to have been so raised and so denudated of their superincumbent 
strata, by some astonishing power, in Derbyshire, Staffordshire, and 
other adjacent counties, as to give the opportunity of examining the 
out-crop, or appearance on the surface, of these strata, which were 
originally covered by all the strata which have been enumerated above. 
The last discovered, entrochal, limestone of Derbyshire, must have 
originally lain, according to Mr. Farey’s calculation, three miles per- 
pendicularly lower than the upper part of the chalk strata. 
Previously to considering more particularly the superior strata, it is 
necessary to make a few remarks on these strata of coal and of lime- 
stone, which appear originally to have existed at such considerable 
depths. The coal measures, according to the observations of Mr. 
Farey, when found at or near the surface, are in situations in which, 
by the agency of that unknown power just alluded to, the strata which 
had lain over them has been removed*. Coal, as I have already en- 
deavoured to show, appears to be the product of vegetable matter, 
buried under particular circumstances, as is almost proved by the 
simple fact of the traces of vegetables being almost constantly dis- 
coverable in it, and in its accompanying strata. If this opinion be 
correct, coal may then have been formed at any period since the 
creation of vegetables ; and of course it would be improper to confine 
its origin, as is done in the first of these volumes, to that period at 
which the deluge occurred which is spoken of by Moses. The obser- 
vations of Werner support this opinion, he having ascertained the 
formation of coal to have taken place at different periods, from that 
formation which rests on the granite rock, and is accompanied b\ 
prophyry and greenstone, to that of bituminous wood, peat, &c. 
* Similar instances of this abstraction of the superior strata which has been observed by Mr. 
Farey, in Derbyshire, have been also discovered by Dr. Richardson, in the basaltic country in 
the counties of Derry and Antrim. Mr. Farey denominates these exposures of the inferior 
strata, denudations; and Dr. Richardson those removals of the superior strata, abruptions.- 
Phil. Trans. 1808. 
