On the Change of Refrangibility of Light. (No. I). Received May 11, - Read May 27, 1852. (+) On the Change of Refrangibility of Light.- No. II. Received June 16, - Read June 26, 1853. (2 Papers).

(London, Richard Taylor and William Francis, 1852 and 1853). 4to. No wrappers as extracted from "Philosophical Transactions" 1852 - Part II. Pp. 463-562 a. 1853 - Vol. 143. Part III. Pp. 385-396. Clean and fine. First appearance of two importent papers in the physical theories of light and the atomic structure."Sir John Herschel first noticed that sulpahte of quinine shows a blue colour when light is incident on it under certain circumstances" later it was found that many other substances, if placed in a dark room and exposed to invisible radiations beyond the viloet end of the visible spectrum, emit a bluish or greenish light. To this phenomenon the name 'flourencence' was given by Stoken in 1852 (the paper offered), in a famous paper disclosing its true nature."(Whittaker in "A History of the Theores of Aether and Electricity" Vol. I.p. 262)."However, long before the discovery of the electron made the compositeness of atoms explicit, the clearest signals that structure was called for came from spectra. Already in 1852, Stokes, in the importent memoir "On the Change of Refrangibility of Ligh" (to which Kelvin referred) had written. "In all probability.the molecular vibrations by which.light is produced are not vibrations i which the molecules move among one another, but vibrations aming the constituent parts of the molecules themselves, performed by virtue of the internal forces which hold the parts of molecules together". Please notice.at that time, the term 'molecule' often meant what we call 'atom'."(Pais in"Inward Bound", p. 175).…