in the sixteenth century. Fully perceiving the importance of the microscope
in studying the nature and origin of such deposits as those of the Pampas,
Darwin submitted many of his specimens both to Dr. Carpenter in this
country, and to Professor Ehrenberg in Berlin. Many very important notes on
the microscopic organisms contained in the formation will be found
scattered through the chapter.

Darwin's study of the older tertiary formations, with their abundant
shells, and their relics of vegetable life buried under great sheets of
basalt, led him to consider carefully the question of climate during these
earlier periods. In opposition to prevalent views on this subject, Darwin
points out that his observations are opposed to the conclusion that a
higher temperature prevailed universally over the globe during early
geological periods. He argues that "the causes which gave to the older
tertiary productions of the quite temperate zones of Europe a tropical
character, WERE OF A LOCAL CHARACTER AND DID NOT AFFECT THE WHOLE GLOBE."
In this, as in many similar instances, we see the beneficial influence of
extensive travel in freeing Darwin's mind from prevailing prejudices. It
was this widening of experience which rendered him so especially qualified
to deal with the great problem of the origin of species, and in doing so to
emancipate himself from ideas which were received with unquestioning faith
by geologists whose studies had been circumscribed within the limits of
Western Europe.

In the Cordilleras of Northern and Central Chili, Darwin, when studying
still older formations, clearly recognised that they contain an admixture
of the forms of life, which in Europe are distinctive of the Cretaceous and
Jurassic periods respectively. He was thus led to conclude that the
classification of geological periods, which fairly well expresses the facts
that had been discovered in the areas where the science was first studied,