Vol. 46. DECEMBER 1873. No. 308. 



Published the First Day of every Month. — Price 2s. dd. 



THE 

 LONDON, EDINBURGH, and DUBLIN 



PHILOSOPHICAL MAGAZINE, 



AND 



JOURNAL OF SCIENCE. 



Being a Continuation of Tilloch's 'Philosophical Magazine/ 

 Nicholson's 'Journal/ and Thomson's ' Annals of Philosophy/ 



CONDUCTED BY 



SIR ROBERT KANE, LL.D. F.R.S. M.R.I.A. F.C.S. 

 SIR WILLIAM THOMSON, Knt. LL.D. F.R.S. &c. 



AND 



WILLIAM FRANCIS, Ph.D. F.L.S. F.R.A.S. F.C.S. 



FOURTH SERIES. 



N» 308.— DECEMBER 1873. 



WITH A PLATE, 



Illustrative of Dr. H. Draper's Paper on Diffraction-Spectrum 

 Photography. 



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