Further Note on the Spectrum of Silicium. 407 



/3 Orionis, and are most prominent in y and e Orionis, in which two 

 spectra they are of about equal intensity. 



The lines in Group IV have never been seen in the spark spectrum of 

 silicium when small coil and small jar capacity are used, but with the 

 spark given by the Spottiswoode coil and plate condenser they appear 

 as weak lines. They are not, like the members of Groups II and III, 

 seen in the spectrum from the bulb when a vacuum tube is used, but in 

 that given by the capillary the strongest ones are very prominent, and 

 vie in intensity with the lines of Group III. 



None of them appear in stellar spectra until the level of temperature 

 represented by y Orionis, and in the spectrum of that star only the 

 strongest of the three is with certainty present. At the e Orionis stage, 

 however, they have developed enormously in intensity, and are amongst 

 the most prominent lines in the spectrum. 



The identity of some of the silicium lines in particular those consti- 

 tuting Group III with lines in stellar spectra was subsequently but 

 independently confirmed, and the results published,* by Mr. Lunt, 

 Assistant at the Royal Observatory, Cape of Good Hope. 



The star the spectrum of which he chiefly considered was /3 Crucis, 

 similar to that of y Orionis, the type star in the Kensington classifi- 

 cation. 



The only enhanced line common to the Kensington and Exner and 

 Haschek's lists, which does not appear to be represented in stellar 

 spectra, is that at X 4030 - 0. It is only a weak line in the spark 

 spectrum, and may possibly be due to an impurity, though it has not 

 yet been traced to any other origin. In the Kensington photograph 

 it is a sharply-defined line, and unlike the other silicium lines in 

 appearance. Exner and Haschek, however, record it as a very diffuse 

 line. 



Of the four additional lines given by Exner and Haschek at XX 3883 '46, 

 4021 '0, 4103'7, and 4764-20, none appear in any of the Kensington- 

 photographs, nor are they represented in the spectra of any of the stars 

 included in the discussion. With these facts in view, it would appear 

 extremely doubtful whether they are really due to silicium. 



In a former paper " On the Chemical Classification of the Stars,"! I 

 gave the chemical definition of the various groups. At that time only 

 the stronger lines of silicium included in Group II were known and 

 traced through the stellar genera. 



We are now in a position to revise the chemical definitions, interpola- 

 ting the various groups of silicium lines as they appear in the stellar 

 groups. 



* ' Astropliys. Jour.,' vol. 11, p. 262. 

 f ' ROT. Soc. Proc.,' vol. 65, p. 186. 



