in what a state of uncertainty we are as to this vitally
important problem;" for this time assigned by Prestwich "would be
clearly insufficient to allow for the development of Egyptian
civilization, as it existed 5,000 years ago, from savage and semi-animal
ancestors; as is _proved_ to be the case with the horse, stag, elephant,
ape," and so on. [96] Now Prestwich, we are told elsewhere, is "the
first living authority on the tertiary and quaternary strata." [97] If,
then, astronomical prepossession can reduce 200,000 to 20,000 years, the
sin of theology, which reduces 20,000 to 7,000 is comparatively venial.
Prestwich's two objections are (1) the data of astronomy, and (2) "the
difficulty of conceiving that man could have existed for 80,000 or
100,000 years without change and without progress." The former is "only
one degree less mischievous than the theological prepossession."
However, Prestwich has some "facts" as well as prepossessions, such as
"the rapid advance of the glaciers of Greenland,"[98] which does not
accord with the generalization from the Swiss glaciers;[99] and the
quicker erosion of river valleys, due to a greater rainfall; facts
which, however, are met by "a _minute description_ of the successive
changes by which in post-glacial time the Mersey valley and estuary were
brought into their present condition, with an estimate of the time they
may have required;" which is "in round numbers 60,000 years," as opposed
to Prestwich's 10,000 or 8,000. [100] The 200,000 years for the ice-age
depends chiefly on Croll's theory of secular variation of the earth's
orbitular eccentricity; but we are told it is open to the "objection
that it requires us to assume a periodical succession of glacial epochs"
of which two or three "must have occurred during each of the great
geological epochs. [101] This is opposed to geological evidence." "'Not
proven' is the verdict which most geologists would return." "The
confidence with which Croll's theory was first received has been a good
deal shaken." "We have to fall back, therefore, on the geological
evidence of deposition and denudation ... in any attempt to decide
between the 200,000 years of Lyell and the 20,000 years of
Prestwich." [102]

As to his arguments based on ancient human remains, their value depends
first on the accuracy of his geological conclusions, and then on
preclusion of all possibility of the conveyance of the remains from
upper strata to lower; on the cer