Their horizontal position, and the great depth at which the hatchets are found, together with their number, and the peculiar incrustation and discoloration of each one, as well as their being in company with the bones of the extinct mammalia, make it improbable that they could have been dropped into fissures or sunk there in modern times.[D]

It is undeniable, for example, that the evidence in favour of the derivation of the horse from the later tertiary Hipparion, and that of the Hipparion from Anchitherium, is as complete and cogent as such evidence can reasonably be expected to be; and the further investigations into the history of the tertiary mammalia are pushed, the greater is the accumulation of evidence having the same tendency.