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L. On the Ultraviolet Spectrum of Elementary Silicon. 

 By Professor J. C. McLennan, F.R.S., and Evan 

 Edwakds, M.A., University of Toronto *. 



IN the course of some work by the writers with a fluorite 

 spectograph on the ultraviolet spectrum of mercury, 

 cadmium, and zinc, their attention was drawn to a paper 

 recently published by Sir William Crookes f on " The 

 Spectrum of Elementary Silicon." In this paper the wave- 

 lengths in the spark spectrum of this element are given 

 down to X= 2124*63 A.U. As the only wave-length as yet 

 published for this element, shorter than this limiting one, is 

 one recorded by Eder and Yalenta { at \ — 1929*0 A.U., it 

 was thought that it might be well to examine the spectrum 

 in the region below X = 2125 A.U. This has now been done, 

 and the present paper contains a list of the lines which have 

 been observed down to \= 1812*2 A.U. 



Sir William Crookes in his paper records that the elementary 

 silicon of the highest purity which he was able to obtain was 

 supplied to him by the Carborundum Company at Niagara 

 Falls. He also records that the three samples supplied by 

 them to him gave an analysis 99*56, 99*86, and 99*98 per 

 cent, of silicon, the impurities being titanium, iron, and 

 aluminium. 



On account of these samples being so pure the writers 

 applied to the Manager of the above-mentioned company for 

 a few small pieces, and these were sent to us with the accom- 

 panying statement that they were presumably of as high 

 purity as those with which the observations of Sir William 

 Crookes were made. 



Our experiments were made with these pieces of silicon, 

 and we desire here to acknowledge our indebtedness to the 

 Carborundum Company for their kindness in the matter. 



In making the experiments the spark was obtained from 

 the discharge of two one-gallon leyden-jars charged with a 

 10-inch induction-coil. A great many plates were taken 

 with different pieces of the silicon, and seven of the best of 



* Communicated by the Authors. Read before the Royal Society of 

 Canada, May 26th, 1915. 



f Sir William Crookes, Proc. Roy. Soc. No. A. 621, vol. xc. Aug. 

 1914, p. 512. 



X Eder and Valenta, Atlas Typischer Spectren, Wien, 1911. 



