Paper, 'Absorption spectra thermograms' by [William De Wiveleslie] Abney and [Edward Robert] Festing The authors write: 'When employing a grating for visual work, the choice of a medium which shall absorb the overlapping parts of orders of the spectrum other than that under examination is a comparatively simple affair. When working photographically, however, it becomes necessary to know what invisible rays the medium will cut off.' Annotations in pencil and ink. Subject: Spectroscopy Received 31 December 1884. Read 15 January 1885. A version of this paper was published in volume 38 of the Proceedings of the Royal Society as 'Absorption-spectra thermograms'. 1884