Neil MacGregor's history of the world as told through things. Throughout this week he is examining the global economy of the 19th century - of mass production and mass consumption. Today he is with an instrument that first helped Europeans to navigate with precision around the world - a marine chronometer. The one Neil has chosen actually accompanied Darwin on his great voyage to South America and the Galapagos Islands - a journey that was to help lead him to his revolutionary theories on evolution.

Producer: Anthony Denselow