there is a wide distinction. Evolution of any kind whatever
naturally implies continuity, and this is the fundamental idea of
Lyellian geology.

In spite, however, of this clear and definite conception of natural
and organic evolution, in all those parts of his works dealing with
earth-history, with the stratified rocks and with the organisms
entombed in them, Lyell adopted a plan which has now been
universally abandoned. He began with the most Recent formations and
worked backwards from the known to the unknown. To modern readers
this is perhaps the greatest drawback to his work, since it renders
difficult the study of events in their actual sequence. However, it
must be admitted that, taking into account the state of geological
knowledge before his time, this course was almost inevitable. The
succession of the later rocks was fairly well known, thanks to the
labours of William Smith and others, but in the lower part of the
sequence of stratified rocks there were many gaps, and more
important still, there was no definite base. Although this want of
a starting point has been largely supplied by the labours of
Sedgwick, Murchison, De la Beche, Ramsay, and a host of followers,
still considerable doubt prevails as to which constitutes the
oldest truly stratified series, and the difficulty has only been
partially circumvented by the adoption of an arbitrary base-line,
from which the succession is worked out both upwards and downwards.
So the problem is only removed a stage further back. In the study
of human origins a similar difficulty is felt with special
acuteness; the beginnings must of necessity be vague and uncertain,
and the farther back we go the fainter will naturally be the traces
of human handiwork and the more primitive and doubtful those traces
when discovered.