Spectroscope with seven prism train, 1868

Spectroscope with seven prism train, 1868. This seven-prism spectroscope was made by the London instrument maker John Browning for the English astronomer Sir Norman Lockyer (1836-1920). Lockyer was using it when he discovered an unknown spectral line in the Sun. He attributed this feature to a mystery element which he called Helium; an element that was only discovered on the Earth in 1894. Lockyer also used this spectroscope to observe prominences; flame features on the edge of the Sun that can normally be seen only during solar eclipses. Jules Janssen (1824-1907) at the Paris Observatory had simultaneously discovered this technique of viewing prominences outside of eclipse. In recognition of their achievement, the French government jointly awarded them a medal showing both scientists. ©SSPL/Science Museum