SECT, xxxvii.] THE MILKY WAY. 415 



the 3rd and 4th magnitude, which forms a broad skirt to its 

 southern border like a vast curtain, without an impression 

 amounting almost to conviction, that the Milky Way is not 

 a mere stratum, but annular, or at least that our system is 

 placed within one of the poorer or almost vacant parts of its 

 general mass, and that eccentrically, so as to be much 

 nearer to the region about the Cross, than to that diametri- 

 cally opposite to it." 



Those dark vacuities called " Coal Sacks " by the ancient 

 navigators, which are so numerous between a Centauri and 

 a Antaris are among the most extraordinary phenomena in 

 the southern hemisphere ; they are of intense blackness, 

 though by no means void of extremely small telescopic stars; 

 the darkness arises from the contrast these nearly vacant 

 spaces form with the excessive brilliancy of the surrounding 

 part of the Milky Way, and the sudden sharp transition 

 from light to darkness. The largest and most conspicuous 

 of them is a pear-shaped vacuity close to the Southern 

 Cross. That portion of the Milky Way that is split longi- 

 tudinally through its centre lies between a Centauri and 

 the constellation of Cygnus, the two bands are joined here 

 and there by narrow bridges of condensed stars, stretch- 

 ing across the darker space between them. In Scorpio and 

 Sagittarius, Sir John Herschel describes the Milky Way 

 as composed of definite clouds of light running into clusters 

 of extremely minute stars like sand, not strewed evenly as 

 with a sieve, but as if thrown down by handfuls, and by 

 both hands at once, leaving dark intervals. In this asto- 

 nishing profusion, the stars are of all sizes from the 14th to 

 the 20th magnitude, and even down to nebulosity. After 

 an interval the same profusion is renewed, the stars being 

 inconceivably minute and numerous beyond description 

 they are in millions and millions. 



The most southerly of the two streams of stars which 

 form the Milky Way in this part of the firmament maintains 



