302 



Mr. W. N. Hartley. 



[June 21. 



spectrum was obtained consisting of a beautiful group of lines with 

 three isolated rays. These lines are attributed to silicon, because they 

 are rendered equally well by sodium silicate, sodium fluosilicate, and 

 by hydrofluosilicic acid, the electrodes being either of gold or of carbon. 

 The strength of the lines is proportional to the strength of the hydro- 

 fluosilicic acid solution examined. The fiducial lines of the tin- 

 cadmium alloy and some of the air lines were employed as before in 

 obtaining measurements from which the wave-lengths of the silicon 

 lines were calculated by means of an interpolation curve. Below are 

 given the wave-lengths of the silicon lines, together with their scale 

 numbers referring to their position on the prism spectrum. The 

 scale numbers are comparable with those given in a paper recently 

 submitted to the Royal Society, and are also applicable to my photo- 

 graphs of spectra in the "Journal of the Chemical Society," vol. 41, 

 p. 90. They represent hundredths of an inch and fractions thereof, 

 reckoned from a strong air line with wave-length 4628*9, which is 

 numbered 10. ("Measurements of the Wave-lengths of Lines of 

 High Refrangibility in the Spectra of Elementary Substances " : 

 Hartley and Adeney.) 



The Spectrum of Silicon. 



Scale numbei's. Wave-lengths. 



178-98 



2881 -0 



233-17 



2631 -4 



256-78 



2541 -0 



260-36 



2528 -1 



261-65 



2523 -5 



263-07 



2518-5 



263*98 



2515 -5 



264-44 



2513 -7 



266-54 



2506 -3 



288-00 



2435 -5 



These are the first spectra of boron and silicon obtained from 

 metallic salts. 



In Messrs. Liveing and Dewar's map of the carbon spectrum 

 ("Proc. Roy. Soc," vol. 33, p. 403), I have observed a group of 

 lines not seen in the spectrum of graphite obtained by me (" Journal 

 of the Chemical Society," vol. 41, p. 90), which might be accounted 

 for by a difference in strength of the spark employed. This 

 group, however, resembles in a striking manner the seven lines 

 in the spectrum of silicon. (See the map of the silicon spectrum.) 

 Their wave-lengths are the following— 2541*0, 2528*2, 2523'6, 25187, 

 2515'8, 2514*0, 2506*3. It will be seen by comparison that these lines 

 approximate so closely to those of silicon that the numbers are well 



