I Felt Myself Brought Within Reach of That Great Fact – That Mystery of Mysteries

After finding fossilized sea shells high in the Andes, Darwin returns to the Beagle to find FitzRoy suffering from depression. While in Valparaíso, Darwin experiences earthquakes and their devastating effects. After FitzRoy's recovery, the Beagle travels to the Galápagos Islands where Darwin finds startling revelations.