The Craven fault, for instance, extends for upwards of 30 miles, and
along this line the vertical displacement of the strata has varied
from 600 to 3000 feet. Professor Ramsay has published an account of a
downthrow in Anglesea of 2300 feet; and he informs me that he fully
believes there is one in Merionethshire of 12,000 feet; yet in these
cases there is nothing on the surface to show such prodigious
movements; the pile of rocks on the one or other side having been
smoothly swept away. The consideration of these facts impresses my
mind almost in the same manner as does the vain endeavour to grapple
with the idea of eternity.
I am tempted to give one other case, the well-known one of the
denudation of the Weald. Though it must be admitted that the
denudation of the Weald has been a mere trifle, in comparison with
that which has removed masses of our palaeozoic strata, in parts ten
thousand feet in thickness, as shown in Professor Ramsay's masterly
memoir on this subject. Yet it is an admirable lesson to stand on the
North Downs and to look at the distant South Downs; for, remembering
that at no great distance to the west the northern and southern
escarpments meet and close, one can safely picture to oneself the
great dome of rocks which must have covered up the Weald within so
limited a period as since the latter part of the Chalk formation. The
distance from the northern to the southern Downs is about 22 miles,
and the thickness of the several formations is on an average about
1100 feet, as I am informed by Professor Ramsay.
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