Plate, figures 14-15 showing dahlia juice with water and acid exposed to the sun by M [Mary?] Somerville Figures 14-15 showing the effect of the sun on drops of dahlia juice mixed with water and with acid. Subject: Physics Published in Philosophical Transactions as 'On the action of the rays of the spectrum on vegetable juices. Extract of a letter from Mrs. M. Somerville to Sir J. F. W. Herschel, Bart., dated Rome, September 20, 1845. Communicated by Sir J. Herschel'. Written by Somerville in Rome [Italy]. Communicated by Herschel. Received by the Royal Society on 6 November 1845. Read 27 November 1845. 20 September 1845