bo 



THE POPULAR SCIENCE MONTHLY. 



from inaximum to maximum being about eleven months. During 

 about five months of that time it is completely invisible to the naked 

 eye ; then it begins to appear again, slowly increasing in brightness 

 for some three months, until it shines as a star of the second magnitude, 

 being then as bright as if not brighter than the most brilliant stars in 

 the constellation. It retains this brilliancy for about two weeks, and 



Map 3. 



then begins to fade again, and, in about three months, once more dis- 

 appears. There are various irregularities in its changes, which render 

 its exact period somewhat uncertain, and it does not always attain the 

 same degree of brightness at its maximum. For instance, in 1779, 

 Mira was almost equal in brilliancy to a first-magnitude stai", but fre- 

 quently at its greatest brightness it is hardly equal to an ordinary star 

 of the second magnitude. Mira will attain its greatest brilliancy 

 about the 2d of November, this year. By the aid of our little map 

 you will readily be able to find it. You will perceive that it has a 



