CELESTIAL PHENOMENA. 



tenth part of a second, it will result that the true diamet^ 

 of the star is eleven times greater than that of the Sun( 106 ). 

 The distance of the double star, 61 Cygni, determined by 

 Bessel,has led to an approximate knowledge of the quantity of 

 matter contained in it. Although the portion of the apparent 

 path passed through by the smaller star since Bradley' s obser- 

 vations is not yet sufficiently large to enable us to infer the 

 true path, and its major semi-axis, yet the great Konigsberg 

 astronomer ( 107 ) considers it probable that " the mass of this 

 double star is neither much more nor much less than half 

 the mass of our Sun." This result is from actual measure- 

 ment. Analogies derived from the greater mass of those 

 planets of our solar system which are attended by satellites, 

 and from the fact that Struve has observed the proportion 

 of double stars to be six times greater among the brighter 

 than among the telescopic stars, have led other astronomers to 

 conjecture ( 108 ), that the average mass of the greater number 

 of double stars exceeds the mass of the Sun. On this sub- 

 ject, however, general results are far from being yet attainable. 

 In respect to proper motion in space, our Sun belongs, 

 according to Argelander, to the class of rapidly moving stars. 

 The aspect of the sidereal heavens, the relative position of 

 stars and nebulae, the distribution of the masses of light 

 formed by them, the picturesque beauty, if I may use the 

 expression, of the whole firmament, depend, in the course 

 of thousands of years, conjointly on the actual proper mo- 

 tion in space of stars and nebulse, on the movement of 

 translation of our solar system, on the appearance of new 

 stars, and the extinction or diminution in intensity of the 

 light of others ; and lastly and especially, on the changes 

 which the Earth's axis undergoes from the attraction of the 



