206 CELESTIAL MEASURINGS AND WEIGHINGS. 



already seen that in the former case the distance between 

 the earth and sun would appear under an angle of i"and 

 in the latter o"*54, whence it is easy to conclude that the 

 mean distances of the stars from each other, or the semi- 

 axes of their orbits, are, in the former case about 15, and 

 in the latter about 29I times that distance. The former 

 orbit would be contained between those of Saturn and 

 Uranus : the latter is about the size of that of Neptune. 



(30.) In such orbits, then, gyrating round each other 

 not in the subordinate relation of sun and planet, but 

 as compeers in dignity and on the equal footing of regal 

 splendour ; communicating to each other we know not 

 what benefits, and bound on we know not what errand, 

 are these wonderful sidereal couples journeying onward 

 through space at the respective rates of 920,000 and 

 2,500,000 miles per diem at the very least : for such 

 would be their proper motions were we sure that they are 

 not foreshortened by oblique presentation to our line of 

 sight ! 



(31.) An interesting, and what to many of our read- 

 ers will probably appear a very unexpected, conclusion 

 follows from this determination of the distance of these 

 stars, conjoined with the knowledge so obtained of the 

 periodic times of their orbital motion. It enables us to 

 weigh theiii; that is, to state in numbers the proportion 

 which the totdX ponderable mass or amou?it oi gravitating 

 matter of the two stars of either couple bears to that of 

 the sun, and therefore as a necessary consequence to that 

 of our own globe, and ultimately (if we choose to lux- 

 uriate in the long array of figures in which such a calcu- 



