200 COSMOS. 



the Southern Cross, where it is at its narrowest part, and is 

 only 3 or 4 in width. Soon after this the Milky Way again 

 expands into a bright and broad mass, which encloses /3 Cen- 

 tauri as well as a and /3 Crucis, and in the midst of which lies 

 the black pear-shaped coal-sack, to which I shall more specially 

 refer in the 7th section. In this remarkable region, somewhat 

 below the coal-sack, the Milky Way approaches nearest to 

 the South Pole. 



The above-mentioned bifurcation, which begins at a Cen- 

 tauri, extended, according to older views, to the constellation 

 Cygnus. Passing from a Centauri, a narrow branch runs 

 northwards in the direction of the constellation Lupus, where 

 it seems gradually lost ; a division next shows itself at / 

 Norma3. The northern branch forms irregular outlines till it 

 reaches the region of the foot of Ophiuchus, where it wholly 

 disappears ; the most southern branch then becomes the main- 

 stream, and passes through the Altar and the tail of the Scor- 

 pion, in the direction of the bow of Sagittarius, where it 

 intersects the ecliptic in 276 long. It next runs in an irre- 

 gular patchy and winding stream through Aquila, Sagitta, and 

 Vulpecula up to Cygnus ; between e, a, and y, of which con- 

 stellation a broad dark \acuity appears, which, as Sir John 

 Herschel says, is not unlike the southern coal-sack, and 

 serves as a kind of centre for the divergence of three great 

 streams. 91 One of these, which is very vivid and conspi- 

 cuous, may be traced running backward, as it were, through 

 /3 Cygni and s Aquilae, without, however, blending with the 

 stream already noticed, which extends to the foot of Ophiuchus, 

 A considerable offset or protuberant appendage is also 

 thrown off by the northern stream from the head of Cepheus, 



91 Outlines, p. 531. The strikingly dark spot between 

 a and y Cassiopeise is also ascribed to the contrast with the 

 brightness by which it is surrounded. See Struve, Etudes 

 note 58. 



