238 THE ROYAL SOCIETY OF CANADA 



In taking the photographs the spark spectrum of zinc was first 

 taken on the plate, then the spark spectrum of siHcon and finally 

 the spark spectrum of aluminium. 



The prominent zinc and aluminium lines in the region examined 

 were : 



Zinc lines^ Aluminium lines^ 



A = 2,138-66 A.°U. A = 1,990-57 A.°U. 



02-35 " 35-9 « 



00-06 " 31-15 " 



2,064-32 " 1,862-81 " 



62-08 " 58-2 " 



25-51 " 54-8 " 



and these were used as standards when determining the wave-lengths 

 of the silicon lines. In measuring up a plate the distances of the 

 various zinc, silicon, and aluminium lines from the edge of the 

 plate were carefully measured with a Hilger comparator. The dis- 

 tances of the above-mentioned zinc and aluminium lines, from the 

 edge of the plate were used for the abscissae of a calibration curve and 

 the wave-lengths of the lines as ordinates. This calibration curve 

 was then used to determine the wave-lengths of the silicon lines. 

 Photographs were also taken of the spark spectra of iron and alumin- 

 ium to make certain that no lines of these elements were included in 

 those obtained with the samples of silicon but as we had no samples 

 of titanium at hand we were not able to take the precaution of making 

 absolutely certain that no lines of that element were included in those 

 ascribed to silicon. However, the high purity of the silicon used, 

 and the fact that the same spectrum came out on the plates when 

 different pieces of the metal and different points on the same pièces 

 were used as sparking terminals would seem to guarantee the purity 

 of the spectrum observed. 



^ Eder and Valenta Atlas Typischer Spectren, Wien. 



2 Handke. Inaugural-Dissertation. Berlin, 1909, p. 18. 



