break between formation and formation, that there has been no sudden
disappearance of all the forms of life and replacement of them by
others, but that changes have gone on slowly and gradually, that one
type has died out and another has taken its place, and that thus, by
insensible degrees, one fauna has been replaced by another, are
conclusions strengthened by constantly increasing evidence. So that
within the whole of the immense period indicated by the fossiliferous
stratified rocks, there is assuredly not the slightest proof of any
break in the uniformity of Nature's operations, no indication that
events have followed other than a clear and orderly sequence.

That, I say, is the natural and obvious teaching of the circumstantial
evidence contained in the stratified rocks. I leave you to consider how
far, by any ingenuity of interpretation, by any stretching of the
meaning of language, it can be brought into harmony with the Miltonic
hypothesis.

There remains the third hypothesis, that of which I have spoken as the
hypothesis of evolution; and I purpose that, in lectures to come, we
should discuss it as carefully as we have considered the other two
hypotheses. I need not say that it is quite hopeless to look for
testimonial evidence of evolution. The very nature of the case precludes
the possibility of such evidence, for the human race can no more be
expected to testify to its own origin, than a child can be tendered as a
witness of its own birth. Our sole inquiry is, what foundation
circumstantial evidence lends to the hypothesis, or whether it lends
none, or whether it controverts the hypothesis. I shall deal with the
matter entirely as a question of history. I shall not indulge in the
discussion of any speculative probabilities. I shall not attempt to show
that Nature is unintelligible unless we adopt some such hypothesis. For