Unpublished paper, 'Über den Gebrauch der Theile des Instrumentes zum beobachten verschiedenartiger Farbenspectra' [On the use of the parts of the instrument for observing different color spectra] by Mr [Joseph Ritter von] Fraunhofer 'On the use of the parts of the instrument for observing the spectra of different colours'. Fraunhofer sent this explanation of his optical apparatus used for observing colour spectra along with the apparatus itself as a present to the Royal Society. Second page includes a stamp that reads 'Soc. Reg. Lond. ex dono. Auctoris'. Subject: Physics / Optics [early 19th century]