704 THE UNIVERSE. 



of this class. But in the extreme depth of the heavens 

 there are still a certain number which cannot be resolved. 



Already 4500 nebulae are known. They are scattered 

 through both hemispheres, and the least of them consists 

 of a perfect swarm of suns, for each of their imperceptible 

 stars represents a sun. 



255. The Dumb-Bell Nebula: Constellation of the Fox ( Vulpecula). 



The stars which form the nebulae are so massed together 

 that they cannot be counted with exactness. Astronomers 

 have only been able to calculate approximately the number 

 in several of those which present a globular form. Arago 

 asserts that there are as many as 20,000 in some of those 

 celestial lights which are in appearance not more than one 

 tenth of the magnitude of the moon's disk. 



These bodies are scattered irregularly enough over the 



