40 C. Lyell on the origin of Coal-fields. 
anticipates that the chronological results, derived from such 
sources, will be in harmony with the conclusions to which bo- 
tanical and zoological considerations alone might lead us, and 
that the lapse of years will be found to be so vast as to have an 
important bearing on our reasonings in every department of geo- 
logical science. 
A question may be raised, how far the codperation of the sea 
in the deposition of the Carboniferous Series might accelerate the 
process above considered. The Lecturer conceives that the inter- 
vention of the sea would not afford such favorable conditions for 
the speedy accumulation of a large body of sediment within a 
limited area, as would be obtained by the hypothesis before stated, 
namely, that of a great river entering a bay in which the waves, 
currents, and tides of the ocean should exert only a moderate 
degree of denuding and dispersing power. 
An eminent writer, when criticising, in 1830 Sir Charles Lyell’s 
work on the adequacy of existing causes, was at pains to assure 
his readers, that while he questioned the soundness of the doc- 
trine he by no means grudged any one the appropriation of as 
much as he pleased of that “least valuable of all things, past 
time.” But Sir Charles believes, notwithstanding the admission 
so often made in the abstract of the indefinite extent of past 
time, that there is, practically speaking, a rooted and perhaps un- 
conscious reluctance, on the part of most geologists, to follow out 
to their legitimate consequences the proofs, daily increasing in 
number, of this immensity of time. It would therefore be of no 
small moment could we obtain even an approach to some positive 
measure of the number of centuries which any great operation of 
nature such as the accumulation of a delta or fluviatile deposit 
of great magnitude may require, inasmuch as our conceptions of 
the energy of aqueous or igneous causes or of the powers of 
vitality in any given geological period must depend on the quan- 
tity of time assigned for their development. 
Thus, for example, geologists will not deny that a vertical 
subsidence of three miles took place gradually at the South Jog- 
gins, during the carboniferous epoch, the lowest beds of the c 
only six inches in a century. But the same movement taking 
place in an upward direction would be sufficient to uplift a por- 
ER SE ER RANE oie a ee ee ees 
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