In 1833, Charles Lyell published the final volume of his pioneering trilogy, which Charles Darwin took with him on the Beagle. In it, Lyell describes the composition of the Earth's crust, examines shell fossils, and explains rock stratification, separating geological formations into three periods – primary, secondary and tertiary. He chastises his fellow geologists for preferring to speculate on the possibilities of the past rather than exploring the realities of the present, and shows his readers the importance of testing the validity of scientific claims. Lyell expertly integrates this book with the two earlier volumes, extending his interpretation of his geological findings from his research in Europe, especially at Mount Etna. Volume 3 consists of 26 chapters, a comprehensive index and 93 woodcut illustrations of different rock formations. Lyell writes with infectious enthusiasm, conveying the excitement of his discoveries in this landmark book.