um thickness {111} are forming at the
present time, along with a large but unknown proportion of surface where
the deposits were far below the maximum thickness. This follows, if we
consider that deposit must go on very unequally along different parts of a
coast, owing to the distance from each other of the mouths of great rivers
and the limitations of ocean currents; and because, compared with the areas
over which a thick deposit is forming annually, those where there is little
or none are probably at least twice as extensive. If, therefore, we take a
width of thirty miles along the whole coast-line of the globe as
representing the area over which deposits are forming, corresponding to the
maximum thickness as measured by geologists, we shall certainly over rather
than under-estimate the possible rate of deposit.[42]

Now a coast line of 100,000 miles with a width of 30 gives an area of
3,000,000 square miles, on which the denuded matter of the whole land-area
of 57,000,000 square {112} miles is deposited. As these two areas are as 1
to 19, it follows that deposition, as measured by _maximum_ thickness, goes
on at least nineteen times as fast as denudation--probably very much
faster. But the mean rate of denudation over the whole earth is about one
foot in three thousand years; therefore the rate of maximum deposition will
be at least 19 feet in the same time; and as the total maximum thickness of
all the stratified rocks of the globe is, according to Professor Haughton,
177,200 feet, the time required to produce this thickness of rock, at the
present rate of denudation and deposition, is only 28,000,000 years.[43]

_The Rate of Geological Change Probably Greater in very Remote Times._--The
opinion that denudation and deposition went on more rapidly in earlier
times owing to the frequent occurrence of vast convulsions and cataclysms
was strenuously opposed by Sir Charles Lyell, who so well showed that
causes of the very same nature as those now in action were sufficient to
account for all the phenomena presented by the rocks throughout the whole
series of geological formations. But while upholding the soundness of the
views of the "uniformitarians" as opposed to the "convulsionists," we must
yet admit that there is reason for believing in a gradually increasing
intensity of all telluric action as we go back into past time. This subject
has been well treated by Mr. W. J. Sollas,[44] who shows that, if, as all
physicists