5 io THE POPULAR SCIENCE MONTHLY. 



the two pairs. The northernmost pair is named e u the magnitudes 

 being fifth and sixth ; distance 3", p. 15. The other pair is e 3 , 

 magnitudes fifth and sixth ; distance 2'3", p. 133. Each pair is 

 apparently a binary ; but the period of revolution is unknown. 

 Some have guessed a thousand years for one pair, and two thou- 

 sand for the other. Another guess gives e, a period of one thou- 

 sand years, and c 2 a period of eight hundred years. Hall, in his 

 double-star observations, simply says of each, "A slow motion." 



Purely by guesswork a period has also been assigned to the 

 two pairs in a supposed revolution around their common center, 

 the time named being about a million years. It is not known, 

 however, that such a motion exists. Manifestly it could not be 

 ascertained within the brief period during which scientific obser- 

 vations of these stars have been made. The importance of the 

 element of time in the study of stellar motions is frequently over- 

 looked, though not, of course, by those who are engaged in such 

 work. The sun, for instance, and many of the stars are known to 

 be moving in what appear to be straight lines in space, but obser- 

 vations extending over thousands of years would probably show 

 that these motions are in curved paths, and some of them, per- 

 haps, in closed orbits. 



If now in turn we take our four-inch glass, we shall see some- 

 thing else in this strange family group of e Lyrse. Between e t and 

 eo, and placed one on each side of the joining line, appear two 

 exceedingly faint specks of light, which Sir John Herschel made 

 famous under the name of the debiMssima. They are of the 

 twelfth or thirteenth magnitude, and possibly variable to a slight 

 degree. If you can not see them at first, turn your eye toward 

 one side of the field of view, and thus, by bringing their images 

 upon a more sensitive part of the retina, you may glimpse them. 

 The sight is not much, yet it will repay you, as every glance into 

 the depths of the universe does. 



The other fourth-magnitude star near Vega is , a wide double, 

 magnitudes fourth and sixth ; distance 44", p. 150. Below we 

 find /?, another very interesting star, since it is both a multiple 

 and an eccentric variable. It has four companions, three of which 

 we can easily see with our three-inch ; the fourth calls for the 

 five-inch ; the magnitudes are respectively four, seven or under, 

 eight, eight and a half, and eleven ; distances 45", p. 150 ; 65", p. 

 320 ; 85", p. 20 ; and 40", p. 248. The primary, p, varies from 

 about magnitude three and a half to magnitude four and a 

 half, the period being twelve days, twenty-one hours, forty-six 

 minutes, and fifty-eight seconds. Two unequal maxima and min- 

 ima occur within this period. In the spectrum of this star some 

 of the hydrogen lines and the D 3 line (the latter representing 

 helium, a constituent of the sun and of some of the stars, which, 



