In this volume, excerpted from Charles Darwin: A Celebration of His Life and Legacy (NewSouth Books, 2013), David King documents Darwin's training in geology and his little-known accomplishments as a geologist. Two great 19th-century geologists, Adam Sedgwick (1785-1873) and Charles Lyell (1797-1875), were strong and positive influences on Darwin. Cambridge's Sedgwick showed Darwin the methods of a field geologist, and his inspiring teaching countered Darwin's earlier negative experience with a poor teacher of geology at Edinburgh. Lyell authored Principles of Geology, of which Darwin read Volume 1 while on the voyage of the HMS Beagle (1831-36). Lyell's geological uniformitarianism provided the framework Darwin needed for the vast periods of time for natural selection to produce the biological change and diversity that he observed in the fossil record and in the living world all around him. King tells how Darwin came to write four significant books on geology and then speculates about why Darwin did not pursue his love of geology after returning home from the Beagle's voyage.