T 11 E 

 LONDON, EDINBURGH and DUBLIN 



PHILOSOPHICAL MAGAZINE 



AND 



JOURNAL OF SCIENCE. 



[THIRD SERIES.] 



JUNE 1845. 



LXVII. On the Interference Spectrum, and the Ahsoiylion of 

 the Tithonic Rays, iij/ John William Draper, M.D., 

 Professor of Chemisti'ij in the University of New York^. 



/CHEMISTS are beginning to experience the want of u 

 ^-^ nomenclature applicable to the various facts which have 

 lately been discovered in relation to the action of some of the 

 imponderable principles. Of these several present themselves 

 to us under the form of radiations, it being their function to 

 group and arrange material particles into the various sub- 

 stances which the organic and inorganic kingdoms present. 

 We may therefore conveniently class them, as Sir J. Herschel 

 proposes, under the name of actinic forces, and entitle the 

 science which treats of them actino-chemistry. For voltaic 

 currents some other provision must be made. 



But the progress of science further requires that a general 

 nomenclature should be agreed upon, to mark out apparent 

 subdivisions among these radiant forces. Even though the 

 separate existence of some of them may not as yet be definitely 

 proved, we must have provisional terms to designate distinctly 

 the facts of which we speak. For want of better, I shall con- 

 tinue to use in this memoir those which I have heretofore em- 

 ployed, and speak of four agents existing in the solar beams : — 

 1st, I'ays of light, or photic rays ; 2nd, rays of heat, or thermic 

 rays; 3rd, tithonic rays; 4th, phosphorogenic rays. The va- 

 rious phaenomena and relations of these constitute the science 

 of actino-chemistry. 



In the solar spectrum, as formed by the action of a prism, 

 if we consider any one of the coloured spaces, we cannot define 

 with precision effects there taking place without the aid of an 

 additional nomenclature. Throughout the spectrum each one 

 of the various radiant principles occurs. In the blue space, 

 for example, there is light which gives an impression to our 

 * Communicated by the Author. 



Phil, Mag, S. 3. Vol. 26. No. 175. June 184.5. 2 I 



