Gore — On Knoivn Variable Stars. 165 



region of tlie heavens in the years 945 and 1264, and he therefore 

 anticipated its return in 1872 ; but judging from the recorded dates, 

 its period (if it has one) 'would seem to he over 300 years. As, how- 

 ever, 311 years have now (1883) elapsed, its appearance — if it is to 

 re-appear — will not probably be much longer delayed. According to 

 Schonfeld, the hypothesis of its identity with the Biblical star of the 

 Magi has been supported by Cardanus, Chladni, and Klinkerfues ; 

 and the supposed length of its period, and the suddenness of its out- 

 burst in 1572, would seem to render such a theory very plausible. 



5. T PiscrDu:. — Schonf eld's observations show no regular period, 

 and no remarkable coloxir. A very bright Maximum occurred 1872, 

 December 1 ; and very faint Minima 1869, November 29, and 1870, 

 December 30. 



6. a Cassiopeia. — Schonfeld thinks the apparent light variation 

 is usually within the errors of observation, and considers that the 

 formula given by Argelander is very doubtful. Schmidt states that 

 he can detect no trace of variation, although he has watched the star 

 for several years. Heis gives the variation from 2*2 m. to 2-8 m. 



7. U Cephei. — This very remarkable variable star is identical 

 with DM 81°, 25. Prom his first observations, Ceraski inferred a 

 period of about 10 days. Schmidt, however, by subsequent observa- 

 tions, reduced this to 4*^ 23^ 35"" ; and from further observations at 

 the Harvard College Observatory, U. S. A., it has been proved that the 

 true period is only one half that given by Schmidt, or 2"^ ll*' 47""5. 

 The rapidity of its variation is very great, sometimes exceeding a 

 magnitude in the. course of an hour ! The total variation exceeds two 

 magnitudes. The star belongs to the Algol type, as it remains at its 

 maximum brightness for the greater portion of its period. It then 

 diminishes for a few hours, and as rapidly recovers its light. The 

 star DM 81°, 30, 8-3 m. is within a few minutes of the variable. 

 Knott finds that the period is subject to some irregularities, and that 

 at alternate minima the star varies in brightness to the extent of 

 about 0-3 m. (9*1 to 9"4). As two periods are nearly equal to 5 days, 

 the alternate minima are observable at nearly the same hour in the 

 evening. Thus Knott observed Minima in 1882, April 22, at lO'^ U^S, 

 and April 27, 9'' 54"'3. Erom photometric measurements at Harvard 

 CoUege, Professor Pickering finds a period of 2^ W 49'"-9 E. At 

 minimum the light is only O'll of the maximum light. The decrease 

 and increase of light occupy about 6 hours. The light ceases to di- 

 minish about 1 hour before the minimum, and then remains constant 

 for l-h hours, when it begins rapily to increase. As in the case of 

 Algol, Pickering considers that the variation of light is probably 

 caused by an eclipsing satellite, and that in this case the eclipse is 

 possibly a total one, the light at minimum being that emitted by 



R. I. A. PROC, SER. II., VOL. IV. SCIENCE. Z 



