418 POPULAR SCIENCE MONTHLY. 



tion, in Cepheus, we notice in the micLt of the brighter region a nearly- 

 circular patch several degrees in diameter, in which little light is 

 seen. A little farther along we notice a similar elongated patch in 

 Oygnus lying across the course of the belt. In this region the brighter 

 portions are of great breadth, more than 20°. 



In Cygnus begins the most remarkable feature of the Milky Way, 

 the great bifurcation. Faintly visible near the zenith, as we trace it 

 towards the south, we see it grow more and more distinct, until we 

 reach the constellation Aquila, near the equator. Between Cygnus and 

 Aquila the western branch seems to be the brighter and better marked of 

 the two, and might, therefore, be taken for the main branch. About 

 Aquila the two appear equal, but south of this constellation we see the 

 western branch diverge yet farther toward the west, leaving the gap be- 

 tween it and the eastern yet broader and more distinct than before. 

 This branch finally terminates in the constellation Ophiuchus, while the 

 eastern branch, growing narrower, can still be followed toward the 

 south. 



Between the equator and the southern horizon we have the brightest 

 and most irregular regions of all. Several round, bright patches of 

 greater or less intensity are projected on a background sometimes 

 moderately bright and sometimes quite dark. If the night is quite 

 clear and moonless we shall see that, after a vacant stretch, the western 

 branch seems to recommence just about the constellation Scorpius. In 

 this constellation we have again a bifurcation, a dark region between 

 two bright ones. 



This is. about as far as the object can be well traced in our middle 

 latitudes. From a point of view nearer to the equator it can be traced 

 through its whole extent. South of Scorpius and Sagittarius it becomes 

 broad, faint and diffused through the constellations of Norma and 

 Circinus. It reaches its farthest southern limit in the Southern Cross, 

 where it becomes narrower and better defined. The most remarkable 

 feature here is the 'coal sack/ a dark opening of elliptical shape in the 

 central line of the stream. West and north of this, in the constellation 

 Argo, is the broadest and most diffused part of the whole stream, the 

 breadth reaching fully 30°. Here we again reach the portion which 

 rises above our horizon. 



Eeturning now to our starting point, we shall notice that, as we 

 make our observations later and later in the autumn, the southern 

 part, which we have been mostly studying, is seen night by night 

 lower down in the west, while new regions are coming into view in the 

 northeast and east. These regions rise earlier every evening, and, if 

 we continue our observations to a later hour, we shall see more and 

 more of them above the eastern or southeastern horizon. By mid- 

 winter Cassiopeia will be seen in the northwest, and we can readily trace 



