370 



THE STELLAR UNIVERSE. 



a planet is at such a part of its orbit that both suns lie in nearly the same di- 

 rection as seen from it, both suns will rise and both will set together. There 

 will then be the ordinary alternation of day and night as on the earth, but the 

 day will have more than the usual splendor, being enlightened by two suns. 



In all intermediate seasons the two suns will rise and set at different times. 

 During a part of the day both will be seen at once in the heavens, occupying 

 different places, and reaching the meridian at different times. There will be 

 two noons. In the morning for some time, more or less, according to the 

 season of the year, one sun only will be apparent, and in like manner, in the 

 evening the sun which first rose will be the first to set, leaving the dominion 

 of the heavens to its splendid companion. 



The diurnal and annual phenomena incidental to the planets attending the 

 central sun S, will not be materially different, except that to them the two suns 

 will have extremely different magnitudes, and will afford proportionally differ- 

 ent degrees of light. The lesser sun will appear much smaller, both on ac- 

 count of its really inferior magnitude and its vastly greater distance. The two 

 days, therefore, when they occur, will be of very different splendor, one 

 being probably as much brighter than the other as the light of noonday is to 

 that of full moonlight, or to that of the morning or evening twilight. 



But these singular vicissitudes of light will become still more striking when 

 it is remembered that the two suns diffuse light of different colors. Let us 

 examine the very common case of the combination of a crimson with a blue sun. 

 In general they will rise at different times. When the blue rises, it will for a 

 time preside alone in the heavens, diffusing a blue morning. Its crimson com- 

 panion, however, soon appearing, the lights of both being blended, a white day 

 will follow. As evening approaches, and the two orbs descend toward the 

 western horizon, the blue sun will first set, leaving the crimson one alone in 

 the heavens. Thus a ruddy evening closes this curious succession of varying 

 lights. As the year rolls on, these changes will be varied in every conceivable 

 manner. At those seasons when the suns are on opposite sides of a planet, 

 crimson and blue days will be alternate, without any intervening night ; and at 

 the intermediate epochs all the various intervals of rising and setting of the 

 two suns will be exhibited. 



" Other suns, perhaps, 

 With their attendant moons, thou wilt descry, 

 Communicating male and female light 

 (Which two great sexes animate the world), 

 Stored in each orb, perhaps, with some that live." 



Paradise Lost, viii., 148. 



PROPER MOTION OF THE STARS. 



In common parlance the stars are said to be fixed. They have received this 

 epithet to distinguish them from the planets, the sun, and the moon, all of 

 which constantly undergo changes of apparent position on the surface of the 

 heavens. The stars, on the contrary, so far as the powers of the eye unaided 

 by art can discover, never change their relative position in the firmament, which 

 seems to be carried round us by the diurnal motion of the sphere, just as if 

 the stars were attached to it, and merely shared in its apparent motion. 



But the stars, though subject to no motion perceptible to the naked eye, are 

 not absolutely fixed. When the place of a star oa the heavens is exactly ob- 

 served by means of good astronomical instruments, it is found to be subject to 

 a change from month to month and from year to year, small indeed, but still 

 easily observed and certainly ascertained. 



It has been demonstrated by Laplace that a system of bodies, such as the 



