Spectroscope, 1872. Instrument of the type developed by Robert Bunsen (1811-1899) and Robert Kirchhoff (1824-1887) during the 1850s. Their work provided a precise tool to make use of Joseph von Fraunhofer's (1787-1826) observatians of dark lines in the solar spectrum (1814). The technique of chemical analysis through spectroscopy has become essential in both terrestrial and astronomical studies. From 'Spectrum Analysis' by H. Schellen. (London, 1872). Photo via Newscom