148 
HAROLD’S DISCUSSIONS. 
really a cluster. Some are double, the smaller revolv¬ 
ing about the larger; others are double-double, one 
two revolving about the other two. 
s 
E 
2T 
Fig. 71.—a Herculis, double star in the telescope, appears 
single to the eye. 
The Milky Way is a part of the sky where the 
stars seem to be crowded together, forming numerous 
clusters. These clusters are arranged in a belt that 
suggests a highway extending obliquely across the sky. 
In places in this belt we may see with the naked 
eye hazy, luminous patches called nebulae. They ap¬ 
pear in many different forms. Herschel examined 
and made drawings of a large number of them, and 
others have since been described (Figs. 9 and 10). 
Some of them make a very beautiful field in the tele- 
