"The similarity of the minerals (both in variety and abundance) of the newer and older formations does not only prove that both were derived from the same source-rocks and that the 'pre-Cambrian' of the southern countries was already uncovered in Neolithic times [Quaternary]. . . , but also that . . . the greater part of the Nile sediments were carried by tributaries draining the Abyssinian Plateau as is the case at the present day."

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