GENERAL SCIENCE 



FIG. 4. A Comet. 



Stars. When we observe the heavens at night, the 

 stars seem to be innumerable, but it is not strictly true 

 to say that the number actually visible to us is countless. 

 There are only about 7000 stars bright enough to be seen 

 with the naked eye under perfect conditions, that is, on a 

 clear, moonless night with the atmosphere free from dust 



