ORIGIN AND NATURE OF COAL. 83 
have resulted from the foliage and branches of a prostrate 
forest, overwhelmed and buried beneath the transported 
detritus of distant rocks. 
These phenomena may be explained by supposing the 
inundation of a thickly-wooded plain from an irruption of 
the sea ; or of a vast inland lake, occasioned by the sudden 
removal of some barrier; or by a subsidence of the tract of 
country on which the forest grew. But when we find an 
accumulation of strata, in which triple deposits of this ° 
kind are repeated some thirty or forty times through a 
thickness of many thousand feet, this solution of the pro- 
blem is not satisfactory. Not only subsidence after sub- 
sidence must have taken place, but the first submergence 
have been followed by an elevation of the land—another soil, 
fit for the growth of forest trees, must have been produced— 
another generation of vegetables, of precisely the same 
species and genera, have sprung up, and arrived at maturity 
—and then another subsidence, and another accumulation 
of drift. And these periodical oscillations in the relative 
level of the land and water must have gone on uninter- 
ruptedly through a long period of time, not in one district 
or country only, but in various parts of the world, during 
the same geological epoch. At present I do not think we 
have data sufficient to explain these phenomena; what has 
been advanced may, perhaps, serve to elicit further informa- 
tion, by pointing out the difficulties in which the question 
is involved, and showing what interesting fields of discovery 
are still unexplored, and how comprehensive and important 
are the objects that come within the scope of geological 
investigation.* 
I will conclude this chapter with the following beautiful 
reflections of Dr. Buckland on the origin and nature of Coal, 
* T would refer the student for a fuller consideration of the phe- 
nomena thus briefly noticed, to the 6th edition of my Wonders of 
Geology, pp. 669, 718, 731. 
