No tools have yet been met with in any of the gravels occurring at the higher levels of the valley of the Seine; but no importance can be attached to this negative fact, as so little search has yet been made for them.

Life Letters and Journals of Sir Charles Lyell 1. One of the contributions that Lyell made in Principles was to explain the cause of earthquakes. Both Whewell and Sedgwick wrote worried letters to him about this.

Lyell was a close and influential friend of Charles Darwin. He is best known as the author of Principles of Geology which popularised James Hutton's concepts of uniformitarianism – the idea that the earth was shaped by the same processes still in operation today.