220 Prof. A. Fowler. The Spectra of Antarian Stars [Feb. 18, 



The most extensive series of visual observations of the Antarian 

 stars were made by Vogel* and Dun erf many years ago, and for the 

 part of the spectrum extending from near D to the extreme red, no 

 other measurements have yet been published. For the region more 

 refrangible than D, however, wave-lengths derived from photographs 

 are available, the most complete statements of these being due to 

 Father Sidgreaves| and Mr. Stebbings.§ The individual results given 

 by different observers vary considerably : visual observations are 

 difficult, and, in the case of photographs taken with prismatic cameras, 

 errors doubtless arise through the lack of suitable reference lines. 

 There is also some difficulty in deciding where a fluting actually 

 commences. The evidence in favour of a titanium origin for most of 

 the flutings, however, depends on such a large number of coincidences 

 that it is almost independent of a very precise knowledge of wave- 

 lengths. 



The flutings in question come out in the arc spectrum of titanium 

 oxide, if the precaution be taken to provide a liberal supply of 

 material and to use a very long arc, taking care also that the image 

 of the "flame" is projected on the slit of the spectroscope. They are 

 also seen in the arc spectrum of the chloride under similar conditions. 

 ^Numerous lines accompany the flutings produced in this manner and 

 some of the details are consequently masked or not recognized without 

 careful study of the photographs. 



So far the flutings have not been very successfully produced in the 

 oxy hydrogen flame; they are visible in the flame spectrum of the 

 fumes from the chloride, but their observation is difficult on account 

 of the bright continuous spectrum. 



The best representation of the flutings has been obtained by passing 

 a spark, without jar, through the fumes of oxy chloride which rise from 

 the chloride of titanium on exposure to air. Under these circumstances 

 the lines which appear are not numerous, and some of the secondary 

 flutings which are masked by lines in the spectrum of the flame of the 

 arc are readily detected, in spite of the continuous spectrum which 

 is also present. The few lines which do appear in this spectrum are 

 probably low temperature lines which may be found of special import- 

 ance in the cooler stars. 



Photographs have been taken over the region C to K, the instrument 

 employed being one built up on the Littrow principle, having one 

 prism of 60°, || and a 2-inch objective of 40 inches focal length, giving 

 a linear dispersion from D to K of 5 inches. Wave-lengths were 



* ' Beobachtungen zu Bothkamp,' toI. 1, p. 20, etc. 



f ' Stir les Etoiles a Spectres de la Troisieme Classe'; " K. Sven. Vet.-Aiad. 

 Hand.," toI. 21, No. 2, 1884. 



X ' Monthly Notices, R.A.S.,' toI. 58, p. 344 ; vol. 59, p. 509. 

 § ' Lick Observatory Circular,' No. 41, May, 1903. 

 || Lent by the Grorernment Grant Committee. 



