1882.] 



On Spectrum Photography. 



81 



June 15, 1882. 



THE PRESIDENT in the Chair. 



The Presents received were laid on the table, and thanks ordered 

 for them. 



Mr. Gabriel Auguste Daubree (Foreign Member), Dr. George 

 Stewardson Brady, Dr. George Buchanan, Mr. Francis Darwin, Pro- 

 fessor William Dittmar, Dr. Walter Holbrook Gaskell, Mr. William 

 Davidson Niven, and Mr. Robert Henry Inglis Palgrave were admitted 

 into the Society. 



The President read a despatch from H.M. Consul- General at 

 Florence, transmitted through the Foreign Office, giving an account 

 of a commemoration in honour of the late Charles Darwin, held in 

 the great hall of the Istituto di Studi Superiori. 



A preliminary (oral) Statement of Results of observation of the 

 total Eclipse of the Sun on May 17, as seen in Egypt, was made by 

 Mr. J. 1ST. Lockyer, F.R.S. 



The following Papers were read : — 



I. " Researches on Spectrum Photography in relation to New 

 Methods of Quantitative Chemical Analysis." By W. N, 

 Hartley, F.R.S.E., &c, Professor of Chemistry, Royal 

 College of Science, Dublin. Communicated by Professor 

 G. G. Stokes, Sec. R.S. Received May 19, 1882. 



Preliminary Note. 



(1.) Since I perfected the instrument employed by me in investi- 

 gating the molecular structure of organic compounds, I have been 

 engaged in studying the spark spectra of elementary bodies with the 

 object of applying my method of working to the purposes of technical 

 chemical analysis. Progress in the course of this research has proved 

 it to be necessary to investigate all kinds of spectra de novo in the 

 hitherto little explored ultra-violet region. 



Some fourteen years' practice in photography has convinced me 

 that when a plate is properly exposed the development of the image 

 is the simplest of all operations ; in order, therefore, to simplify spec- 

 troscopic work, I have carefully ascertained the time of exposure 

 required to produce the most characteristic spectra under various 



VOL. xxxiv. G 



