GEOLOGY

Darwin began his voyage by reading Charles Lyell’s (1779–1875)
Principles of Geology. In this book, Lyell developed the ideas of another
geologist, James Hutton, into the theory of uniformitarianism.
His theory was based on the idea that the forces of wind, rain,
rivers, volcanoes, and geological uplift shape the earth today, just
as they have in the past. Lyell and Hutton contended that it was
these forces, not catastrophic events, that shaped the face of the
earth over hundreds of millions of years. This book planted two
important ideas in Darwin’s mind: (1) the earth could be much
older than 6,000 years, and (2) if the face of the earth changed
gradually over long periods, could not living forms also change
during that time?