ASTKONOMY. 141 



tbe sccoikT iunl ninth niagfnitudes. An important result of Lis obser- 

 vations is the intimate connection shown between tlie lengtli of period 

 and the depth of color of the star ; the very short-period variables are 

 nearly white; those of longer period somewhat redder, the tint grow- 

 ing deeper, the longer the i)erioil. 



Several new variable stars have been detected by Chandler, Saw-yer, 

 Esi)iu, and others, and among them are two of more than ordinary in- 

 terest, as they apparently belong to the well-known "Algol-type." The 

 lirst was discovered by Mr. Chandler in the constellation Cygnus (Y 

 Cygni), right ascension =20'' 47"'.5; declination =+310 14' (DM. 4- 

 340, 4181). Its light varies from 7.1 magnitude to about 7.9 magni- 

 tude, and the period is probably 1*^ 11'" 50'" 48^ The second star re- 

 ferred to, was discovered by Mr. Sawyer in March, 1887, in the constel- 

 lation Canis Major, and as it is the first undoubted variable found in 

 that constelhition, it will probably be known as U Canis Majoris. Its 

 position for 1887 is right ascension =7'' 14"\4; declination = — 10° 11'. 

 The minimum observed by Mr. Sawyer was G.7 magnitude, and the 

 ])eriod is 1*^ 3'' 15'" ijii'*. Mr. Chandler has colle(;ted the observations of 

 U Oi)hiuchi, of all variables the one with shortest period and the most 

 rapid fluctuations of light, and he finds a curious but well-marked re- 

 tardation in the increase of brilliancy some half-hour or so after mini- 

 uuim is passed. A similar irregularity has been noticed in the light- 

 curve of S Cancri and occasionally in that of Algol. 



Mr. Chandler strongly urges the possessors of large refractors to 

 devote a portion of their time to the observation of the minima of vari- 

 ables that become too faint lor ordinary telescopes, our knowledge of 

 such variables being extremely deficient. Argelander's method of ob- 

 servation is recommended. 



Professor Pickering has in preparation fin index to observations of 

 variable stars which will give for each star the number of observations 

 each year since the discovery of variability. This index will be pub- 

 lished in volume 18 of the Annals of the Harvard Observatory. 



In an interesting article published in the Observatory (April, 1888), 

 Miss Clerke has collected a series of notes upon variable double stars. 

 These stars show- for the most part a spectrum analogous to that of 

 Sirius, that is of Class I, although single stars of that class hardly ever 

 show any fluctuations in brightness. Algol-variables, if the eclipse 

 theory of their changes be admitted, make no exceptions to this rule; 

 Gore's catalogue contains three exami)les: cJ Orionis, S Monocerotis, 

 and Y Virgims, and among the well-known doubles are y Virginis, 

 C Bootis, TT Boot is, 38 (leminorum, a' Piscium, ff Serpentis, and /:; Scor- 

 pii, and i)erha[)S 6 Cygui. With few and doubtful exceptions, revolv^- 

 ing double stars vary in concert, if they vary at all. The changes of 

 y Virginis illustrate the mode of procedure in this respect of couples 

 iiitiinsically ecpuil. They alternate in each (;()mi)onent, and can thus 

 b(^ detected only by close attention, i'^ach may be described as nor- 



