F3407

Achromatic convex burning lens by Dollond in a mahogany frame Long Caption: It was used by William Herschel in his study of the properties of 'radiant heat'. In observing the Sun, William Herschel tried a number of different colour filters to protect his eyes and found that the different colours seemed to block out different amounts of heat as well as light. In order to assess the relationship between heat and light he decided to test if heat showed any of the same properties as light by using this lens to focus the heat onto a thermometer. This experiment showed that heat, like light, could be refracted. Credit line: © National Maritime Museum, Greenwich, London, Herschel Collection Object: AST0784 Artist: Dollond Date: 1798-1800 Medium: glass; mahogany; brass Size: 532 mm x 892 mm x 229 mm Click here to buy a bespoke print of this image.