onsiderations which have been advanced by Lyell and Darwin.
The former says:--

The total absence of any trace of fossils has inclined many
geologists to attribute the origin of the most ancient strata to an
azoic period, or one antecedent to the existence of organic beings.
Admitting, they say, the obliteration, in some cases, of fossils by
plutonic action, we might still expect that traces of them would
oftener be found in certain ancient systems of slate, which can
scarcely be said to have assumed a crystalline structure. But in
urging this argument it seems to be forgotten that there are
stratified formations of enormous thickness, and of various ages,
some of them even of tertiary date, and which we know were formed
after the earth had become the abode of living creatures, which
are, nevertheless, in some districts, entirely destitute of all
vestiges of organic bodies[54].

[54] _Elements of Geology_, p. 587.

He then proceeds to mention sundry causes (in addition to plutonic
action) which are adequate to destroy the fossiliferous contents of
stratified rocks, and to show that these may well have produced enormous
destruction of organic remains in these oldest of known formations.

Darwin's view is that, during the vast ages of time now under
consideration, it is probable that the distribution of sea and land over
the earth's surface has not been uniformly the same, even as regards
oceans and continents. Now, if this were the case, "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 naked 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 Cambrian epoch in a completely
metamorphosed and denuded condition[55]." The probability of this view
he sustains by certain general considerations, as well as particular
facts touching the geology of oceanic islands, &c.

[55] _Origin of Species_, p. 289.

On the whole, then, it seems to me but reasonable to conc