Charles Lyell, Historian of Time's Cycle - Time's Arrow, Time's Cycle: Myth and Metaphor in the Discovery of Geological Time - page 121

especially floods, earthquakes, and eruptions. But these catastrophes are strictly local;
they neither occurred in the past, nor shall happen in the future, at any greater frequency
or extent than they display at present. In particular, the whole earth is never convulsed
at once, as some theorists held. Speaking of floods, for example, Lyell writes:
They may be introduced into geological speculations respecting the past, provided we
do not imagine them to have been more
Figure 4.4
A classic example of Lyell's gradualism—the "denudation of the Weald." The
geological structure of this eroded basin (top) is a great dome, bowed up after
deposition of the Chalk in Cretaceous times (number 1 in both figures). The bottom
figure represents the dome soon after its formation, with breakage and erosion just
beginning in chalk deposits at the dome's summit. The top figure shows that, by gradual
erosion of the Chalk and underlying layers, the modern basin has formed, with a
substantial separation (by denudation) of the North and South Downs (the upstanding
sides of the original dome, labeled as number 1). Lyell's premier example of gradualism
led Darwin into one of his most famous errors. In the first edition of the Origin of
Species, he used the denudation of the Weald to illustrate the insensible slowness of
gradual change in geology. He estimated the time required for this denudation as 300
million years (though the actual time since deposition of the Chalk is only 60 million
years or so). In later editions, Darwin dropped this calculation after receiving severe
criticism. (Illustrations from the first edition of Lyell's Principles. )