Charles Withers, Professor Emeritus University of Edinburgh and Geographer Royal for Scotland reading from a letter to Darwin by Lyell discussing the domestication of the dog.

Sir Charles Lyell was a geologist whose work helped to found the modern notion of geology and geologic time whilst establishing geology as a separate science. In his first book, Principles of Geology, (1830) he propounded his theory of uniformitarianism, that the Earth's history can be explained by gradual change over time. He also proposed the idea that different periods of geologic time could be established by reference fossils, he divided geologic time into four periods; Pleistoscene, Older Pliocene, Miocene and Eocene. He also expounded notions on the rock cycle, how one type of rock was transformed into another, volcanic forces, deposition and erosion.