470 THE POPULAR SCIENCE MONTHLY. 



The nearest pair revolve around their common center in about 

 fifty-eight years, while the third star revolves with the other two, 

 around a center common to all three, in a period of six or seven 

 hundred years. But the movements of the third star are erratic, 

 and inexplicable except upon the hypothesis advanced by Seeliger, 

 that there is an invisible, or dark, star near it by whose attraction 

 its motion is perturbed. 



In endeavoring to picture the condition of things in t Cancri 

 we might imagine our sun to have a companion sun, a half or a 

 third as large as itself, and situated within what may be called 

 planetary distance, circling with it around their center of gravity ; 

 while a third sun, smaller than the second and several times as 

 far away, and accompanied by a hlack or non-luminous orb, swung 

 with the first two around another center of motion. There you 

 would have an entertaining complication for the inhabitants of a 

 system of planets ! 



Other objects in Cancer are : 2 1223, double star, magnitudes 

 six and six and a half, distance 5", p. 214 ; 2 1291, double, magni- 

 tudes both six, distance 1*3", p. 328^ four-inch should split it ; 

 I, double, magnitudes four and a half and six and a half, distance 

 30", p. 308 ; GG, double, magnitudes six and nine, distance 4"8", 

 p. 136; 2 1311, double, magnitudes both about the seventh, dis- 

 tance 7", p. 200 ; 1712, star cluster, very beautiful with the five- 

 inch glass. 



The constellation of Auriga may next command our attention 

 (map No. 5). The calm beauty of its leading star Capella awakens 

 an admiration that is not diminished by the rivalry of Orion's 

 brilliants glittering to the south of it. Although Capella must be 

 an enormously greater sun than ours, its spectrum bears so much 

 resemblance to the solar spectrum that a further likeness of con- 

 dition is suggested. No close companion to Capella has been dis- 

 covered, and it is not probable that any exists except, possibly, in 

 the form of planets which no telescope can reveal. A ninth-mag- 

 nitude companion, distant 159", p. 146, and two others, one of 

 twelfth magnitude at 78", p. 317, and the other of thirteenth mag- 

 nitude at 126", p. 183, may be distant satellites of the great star, 

 but not planets in the ordinary sense, since it is evident that 

 they are self-luminous. It is as ignificant fact that most of the 

 first-magnitude stars have faint companions which are not so 

 distant as altogether to preclude the idea of physical relation- 

 ship. 



While we are in Auriga we must look at the star P (Menka- 

 lina), which belongs to a peculiar order of double stars discovered 

 within the past few years. But neither our telescopes, nor any 

 telescope in existence, can directly reveal the duplicity of p Au- 

 rigse to the eye i. e., we can not see the two stars composing it. 



