PROCEEDINGS OF THE ACADEMY AND AFFILIATED 



SOCIETIES 



PHILOSOPHICAL SOCIETY OF WASHINGTON 



The 809th meeting of the Society was held at the Administration 

 Building of the Carnegie Institution, November 23, 1918; Vice-Presi- 

 dent Humphreys in the chair; 50 persons present. 



Mr. W. F. Meggers presented the first paper on Photography of the 

 red and infra-red solar spectrum. This paper was illustrated by lantern 

 slides. 



Ordinary photographic plates stained with dicyanin have been used 

 extensively for several years at the Bureau of Standards in recording 

 the arc spectra of metals and tube spectra of gases in the red and adja- 

 cent infra-red spectral regions. The spectra of about half of the chem- 

 ical elements have thus been investigated from the yellow at wave- 

 lengths of about 6000 A into the infra-red to about 9000 A, and in some 

 cases to wave-lengths greater than 10,000 A. 



This success in photographing the long waves from artificial sources 

 suggested an attempt to photograph the infra-red solar spectrum 

 on dicyanin stained plates, for, up to the present time, no complete 

 or accurate determinations of wave-lengths corresponding to Fraun- 

 hofer lines in the infra-red have existed, and there have been scarcely 

 any reliable measurements in spectra of the chemical elements in this 

 same region; identifications of absorption and emission lines have, 

 therefore, been few and uncertain. 



This work was first undertaken at the Johns Hopkins University in 

 April, 191 7, and a brief account of it was published in the Astrophysical 

 Journal^ together with a map of the solar spectrum from 6860 A to 

 9600 A. Over 2000 Fraunhofer lines were measured between wave- 

 lengths limits and about 400 of them were identified with emission 



^ Meggers. Astrophys. Journ. 47: i. 1918. 



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