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Y. Measurements of the Wave-lengths of Lines of High Refrangibility in the Spectra 
of Elementary Substances. 
By W. N. Hartley, F.R.S.E., &c., Professor of Chemistry, Royal College of Science, 
and W. E. Adeney, F.C.S., Associate of the Royal College of Science. Dublin. 
Communicated by Professor Stokes, LL.D., Sec. R.S. 
Received March. 20,— Read April 19, 1883. 
[Plates 4-6.] 
Introduction. 
In the Philosophical Transactions, Vol. 170, pp. 257-274, 1879, one of us has described, 
in conjunction with Mr. A. K. Huntington, the first use of dry gelatine films, sen¬ 
sitised with silver bromide, for photographing ultra-violet spectra ; and the application 
of the almost continuous spectrum emitted by the metals iron, nickel, and copper to 
the purpose of examining the ultra-violet absorption spectra of organic compounds. 
These researches, up to the present* time, have been prosecuted under considerable 
disadvantages, owing to the impossibility of describing accurately either absorption or 
emission spectra, by reason of the data for calculating wave-lengths being unfor¬ 
tunately insufficient. The object of this work is to give an exact description of the 
photographed spectra of some sixteen elementary substances, and to place on record the 
wave-lengths of so large a number of well-defined metallic lines, together with such 
other measurements of spectra, that subsequent workers may experience no difficulty in 
constructing interpolation curves capable of yielding fairly accurate numbers repre¬ 
senting wave-lengths. The first measurements of rays of high refrangibility made by 
means of photography were the determinations of the wave-lengths of the lines of 
cadmium by M. Mascart (‘Annales de l’Ecole Normale,’ vol. iv., 1867). He made 
use of a Nobert’s grating, a goniometer, and a photographic eye-piece. In addition 
to the splendid map of the ultra-violet portion of the solar spectrum given us by 
M. Cornu, we have wave-lengths most carefully calculated for a series of lines in the 
spectra of the metals cadmium, magnesium, aluminium, and zinc (‘ Annales de l’Ecole 
* Proc. Roy. Soc., xxxi., pp. 1-26. Journ. Cliem. Soc., xxxix., pp. 57-60, and pp. ] 11-128; xxxvii., 
pp. 676-678, &c. 
