1-158-589 - Oxford Science Archive/Heritage Images

Gustav Kirchhoff, Robert Bunsen and Henry Roscoe, scientists, c1860. Left to right: Gustav Robert Kirchhoff (1824-1887), German physicist; Robert Wilhelm Eberhard von Bunsen (1811-1899), German physicist and chemist; Henry Enfield Roscoe (1833-1915), English chemist. From History of Chemistry by Edward Thorpe. (London, 1910). Kirchhoff and Bunsen's collaboration on spectrum analysis led, in 1859, to the discovery of caesium and rubidium. Roscoe was also a collaborator and friend of Bunsen, the two notably working together on comparative photochemistry.