that things have thus remained from the beginning of
this world? Our continents seem to have been formed by a preponderance,
during many oscillations of level, of the force of elevation; but may not
the areas of preponderant movement have changed in the lapse of ages? At a
period immeasurably antecedent to the silurian epoch, continents may have
existed where oceans are now spread out; and clear and open oceans may have
existed where our continents now stand. Nor should we be justified in
assuming that if, for instance, the bed of the Pacific Ocean were now
converted into a continent, we should there find formations older than the
silurian strata, supposing such to have been formerly deposited; for it
might well happen that strata which had subsided some miles nearer to the
centre of the earth, and which had been pressed on by an enormous weight of
superincumbent water, might have undergone far more metamorphic action than
strata which have always remained nearer to the surface. The immense areas
in some parts of the world, for instance in South America, of bare
metamorphic rocks, which must have been heated under great pressure, have
always seemed to me to require some special explanation; and we may perhaps
believe that we see in these large areas, the many formations long anterior
to the silurian epoch in a completely metamorphosed condition.

The several difficulties here discussed, namely our not finding in the
successive formations infinitely numerous transitional links between the
many species which now exist or have existed; the sudden manner {311} in
which whole groups of species appear in our European formations; the almost
entire absence, as at present known, of fossiliferous formations beneath
the Silurian strata, are all undoubtedly of the gravest nature. We see this
in the plainest manner by the fact that all the most eminent
palaeontologists, namely Cuvier, Agassiz, Barrande, Falconer, E. Forbes,
&c., and all our greatest geologists, as Lyell, Murchison, Sedgwick, &c.,
have unanimously, often vehemently, maintained the immutability of species.
But I have reason to believe that one great authority, Sir Charles Lyell,
from further reflexion entertains grave doubts on this subject. I feel how
rash it is to differ from these authorities, to whom, with others, we owe
all our knowledge. Those who think the natural geological record in any
degree perfect, and who do not attach much weight to the facts and
argu