34 



SCIENCE 



[N. S. Vol. XXXVII. No. 940 



constant minimum brightness, lasting about 3 J 

 hours, during which the magnitude is 13.50. The 

 duration of eclipse is 8i hours. The light change 

 is very rapid, the last magnitude of the descent is 

 aceomplished in 20 minutes. For two magnitudes 

 of the descent the visual and photographic curves 

 are in close agreement, but from this point the 

 photographic variation seems more rapid than the 

 visual. For Am = 3.25 mags, visually, the photo- 

 graphic value is 3.50. This greater photographic 

 range is probably real. The observed time of 

 minimum was eleven minutes late of the ephemeris 

 from the elements of the Laws Observatory Bul- 

 letin No. 9, indicating a correction to the period, 

 which is slightly less than 2'' 20", of less than a 

 second. 

 Spectro graphic Observations of <t> Fersei: Frank 



C. JOEDAN. 



This star has been known, since 1889, to have a 

 bright line spectrum. About 400 spectrum plates 

 have been obtained by various observers, and its 

 period determined as 126.5 days. The hydrogen 

 lines are constituted as follows: A broad, weak, 

 underlying absorption, upon which is superposed a 

 broad emission line appearing as two because of 

 a central narrow and strong absorption. The 

 sharpness and strength of the absorption lines 

 varies strikingly in different parts of the orbit, 

 becoming at one phase so weak and diffuse as to 

 be almost immeasurable. Helium lines show only 

 at certain phases. There are visible at least 

 twelve other bright lines which seem to be con- 

 stituted like the hydrogen lines, and to give the 

 same velocity as these lines. 



The velocity curve is peculiar in that at about 

 one third of the period from maximum positive 

 velocity there is a decided hump. The highest 

 velocity is + 44 km. It goes down to — 7 km. 

 at phase 24 days, up to km. at phase 35 days, 

 then down to a minimum of — 21 km. at phase 

 75 days. In different revolutions of the system 

 the velocity curves do not seem to be the same 

 either in shape or amplitude. 



Preliminary measures on the bright hydrogen 

 lines give a velocity curve different from that of 

 the absorption lines, but not such a curve as would 

 be given by a secondary body. 

 Spectro graphic Observations of Algol: Frank 



SCHLESINGER. 



Algol has been upon the observing list for the 

 Mellon spectrograph during the past six years. 

 A total of 336 spectrograms have been secured, 

 and have been measured and reduced by the 



author under as uniform conditions as possible. 

 A study of this material yields the following chief 

 results: (1) The long period oscillation in the 

 radial velocities, announced by Belopolsky in 1906, 

 is unmistakably confirmed. This oscillation has a 

 period of 1.874 years and a semi-amplitude of 

 9.14 km., and is in an orbit whose eccentricity is 

 small. (2) Such an oscillation should be accom- 

 panied by a similar oscillation in the times of light 

 minimum, the latter sometimes occurring as much 

 as 5 minutes in advance and sometimes 5 minutes 

 after the predicted epochs. An examination of 

 the rich photometric material on this star obtained 

 in the years from 1852 to 1887 brings out this 

 small term with almost precisely the amplitude 

 computed from the spectrographic measures. (3) 

 The eccentricity of the short-period orbit (2.87 

 days) comes out small, very probably less than 

 0.02. This seems to make it necessary to reject 

 Tisserand's explanation for Chandler's long-pe- 

 riod term (141 years) in the times at which light 

 minima occur, since this explanation demands an 

 eccentricity in the neighborhood of 0.13. A re- 

 newal of photometric observations of Algol is 

 much to be desired, as well as a rediseussion of all 

 the available data of this kind. 

 The Orbit of X Tauri: Frank Schlesinger. 



Eighty-nine spectrograms of this bright Algol 

 variable have been secured with the Mellon spec- 

 trograph at the Allegheny Observatory. These 

 yield the following elements of its orbit: period 

 (assumed from photometric data), 3.9529 days; 

 semi-amplitude 58.1 km. ± 1.08 km.; eccentricity, 

 0.053 ±0.017; longitude of periastron, 111°. 6 ± 

 20°. 5; time of periastron passage, 0.31 days 

 after light minimum ± 0.23 days; mean velocity, 

 + 13.6 km. 



The lines in the spectrum of this star are 

 affected by shadings alternately on their red and 

 violet sides. These can not be due to the presence 

 of the fainter spectrum, since they are too close to 

 the lines of the bright spectrum to permit of this 

 explanation. The spectrograms are all upon plates 

 of fine grain. 

 The Magnitude Scale of the Polar Sequence: F. 



H. Seares. 



The methods of photographic photometry em- 

 ployed with the 60-inch reflector of the Mt. Wilson 

 Observatory involve the use of a wire gauze screen 

 and diaphragms of various apertures. The most 

 troublesome difficulty has been the determination 

 of the error depending on the distance of the 

 stars from the axis of the instrument which varied 



