Plate, luminous and photographic spectra by John Frederick William Herschel Plate showing graphite illustrations of luminous and photographic spectra observed by Herschel. Subject: Chemistry Published in Philosophical Transactions as 'On the chemical action of the rays of the solar spectrum on preparations of silver and other substances, both metallic and non-metallic, and on some photographic processes'. Received and read by the Royal Society on 20 February 1840. [1840]