1883.] 



On Line Spectra of Boron and Silicon. 



301 



June 21, 1883. 



THE TREASURER in the Chair. 



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

 for them. 



Professor George Francis Fitzgerald, Dr. Walter Plight, Mr. John 

 Newport Langley, and Mr. John Venn were admitted into the Society. 



The following Papers were read : — 



I. "On Line Spectra of Boron and Silicon." By W. N. 

 Hartley, F.R.S.E., &c, Royal College of Science, Dublin. 

 Communicated by Professor Stokes, Sec. R.S. Received 

 May 28, 1883. 



In the conrse of an extended examination of all varieties of saline 

 solutions by means of the spark and a photographic camera, I have 

 observed two spectra of much interest. I detach my notes from the 

 paper in which they are embodied in order to give them an earlier 

 publication. 



Boron. — In order to ascertain whether sodium borate would yield 

 any spectrum beyond that due to sodium, a strong solution of borax 

 was first examined and subsequently a saturated solution of boracic 

 acid. The graphite electrode with which the solution was submitted 

 to the action of the spark, was opposed to a pole of a tin-cadmium 

 alloy, in order that the wave-lengths of any lines that might appear 

 could be determined by reference to those of tin and cadmium. It is 

 a remarkable fact that when a saturated solution of borax is used, the 

 sodium lines are not visible, while there appear three strong sharp 

 lines, which as they are likewise yielded by boracic acid must be con- 

 sidered as characteristic of boron. 



The Spectrum of Boron. 



Scale numbers. 



Wave-lengths. 



96 -18 

 269 -20 



269 "48 



3450 -3 

 2497 -0 

 2496-2 



Silicon. — A strong solution of sodium silicate was in like manner 

 submitted to the action of the spark. There was only a feeble 

 indication of the strongest sodium line (A = 3301), but a strong 



