DISTRIBUTION OF STARS. 13S 



at difierent heights and in various directions over tlie field 

 of view, of 15' in diameter, of his twenty-feet reflecting tel- 

 escope. Frequent reference has already been made in the 

 present work to his laborious process of "gauging the heav- 

 ens." The field of view each time embraced only iraVo oo-^^* 

 of the whole heavens ; and it would therefore require, ac- 

 cording to Struve, eighty-three years to gauge the whole 

 sphere by a similar process.* In investigations of the par- 

 tial distribution of stars, we must specially consider the class 

 of magnitude to which they photometrically belong. If we 

 limit our attention to the bright stars of the first three or 

 four classes of magnitudes, we shall find them distributed on 

 the whole with tolerable uniformity,! although in the south- 

 ern hemisphere, from e Orionis to a Crucis, they are locally 

 crowded together in a splendid zone in the direction of a 

 great circle. The various opinions e?vpressed by different 

 travelers on the relative beauty of the northern and south- 

 ern hemispheres, frequently, I believe, depends wholly on the 

 circumstance that some of these observers have visited the 

 Southern regions at a period of the year when the finest por- 

 tion of the constellations culminate in the daytime. It fol- 

 lows, from the gaugings of the two Herschels in the north- 

 ern and southern hemispheres, that the fixed stars from the 

 fifth and sixth to the tenth and fifteenth magnitudes (par- 

 ticularh^ therefore, telescopic stars) increase regularly in 

 density as we approach the galactic circle (6 yaXa^iag icv- 

 K?.og) ; and that there are therefore poles rich in stars, and 

 others poor in stars, the latter being at right angles to the 

 principal axis of the Milky Way.. The density of the stellar 

 light is at its minimum at the poles of the galactic circle ; 

 and it increases in all directions, at first slowly, and then rap- 

 idly, in proportion to the increased galactic polar distance. 

 By an ingenious and careful consideration of the results 

 of the gauges already made, Struve found that o?i the average 

 there are 29*4 times (nearly 30 times) as many stars in the 

 center of the Milky Way as in regions surrounding the ga- 

 lactic poles. In northern galactic polar distances of 0^, 30°, 

 60^, 75°, and 90°, the relative numbers of the stars in a tel- 

 escopic field of vision of 15' diameter are 4*15, 6*52, 17*6S, 

 30-30, and 122-00. Notwithstanding the great similarity 

 bi the law of increase in the abundance of the stars, we 

 again find in the comparison of these zones an absolute pre« 



* Etudes d'Asir. Stellaire, note 74.. p. 31. 

 + OtiUincs of Ash-., § 78') 



