an important bearing on biological thought and speculation, such as the
proofs of imperfection in the geological record, the relations of the later
tertiary faunas to the recent ones in the same areas, and the apparent
intermingling of types belonging to distant geological epochs, when we
study the palaeontology of remote districts,--there are other purely
geological problems, upon which the contributions made by Darwin are of the
very highest value. I believe that the verdict of the historians of science
will be that if Darwin had not taken a foremost place among the biologists
of this century, his position as a geologist would have been an almost
equally commanding one.

But in the case of Darwin's principal geological work--that relating to the
origin of the crystalline schists,--geologists were not at the time
prepared to receive his revolutionary teachings. The influence of powerful
authority was long exercised, indeed, to stifle his teaching, and only now,
when this unfortunate opposition has disappeared, is the true nature and
importance of Darwin's purely geological work beginning to be recognised.

The two first chapters of the "Geological Observations on South America,"
deal with the proofs which exist of great, but frequently interrupted,
movements of elevation during very recent geological times. In connection
with this subject, Darwin's particular attention was directed to the
relations between the great earthquakes of South America--of some of which
he had impressive experience--and the permanent changes of elevation which
were taking place. He was much struck by the rapidity with which the
evidence of such great earth movements is frequently obliterated; and
especially with the remarkable way in which the action of rain-water,
percolating through deposits on the earth's surface, removes all traces of
shells and other calcareous organisms. It was these considerations which
were the parents of the generalisation that a palaeontological record can