374 COLORS OF THE STARS. SECT. XXXVII. 



If it be considered that all the double stars appear sin- 

 gle to the naked eye, and with ordinary instruments, 

 and that it requires the highest powers of the very best 

 telescopes to separate the greater number of them, the 

 extreme beauty of the ingenuity and refraction necessary 

 to draw such profound results from their motions may 

 be in some degree appreciated. 



The double stars are of various hues, but they most 

 frequently exhibit the contrasted colors. The large star 

 is generally yellow, orange, or red ; and the small star 

 blue, purple, or green. Sometimes a white star is com- 

 bined with a blue or purple, and more rarely a red and 

 white are united. In many cases, these appearances 

 are due to the influence of contrast on our judgment of 

 colors. For example, in observing a double star, where 

 the large one is a full ruby red, or almost blood color, 

 and the small one a fine green, the latter loses its color 

 when the former is hid by the cross wires of the tele- 

 scope. But there are avast number of instances where 

 the colors are too strongly marked to be merely imagi- 

 nary. Sir John Herschel observes in one of his papers 

 in the Philosophical Transactions, as a very remarkable 

 fact, that, although red stars are common enough, no 

 example of a solitary blue, green, or purple one has yet 

 been produced. 



The stars are scattered very irregularly over the fir- 

 mament. In some places they are crowded together, in 

 others thinly dispersed. A few groups more closely 

 condensed form veiy beautiful objects even to the naked 

 eye, of which the Pleiades and the constellation Coma 

 Berenices are the most striking examples ; but the 

 greater number of these clusters of stars appear to un- 

 assisted vision like thin white clouds or vapor : such 

 is the milky way, which, as Sir William Herschel has 

 proved, derives its brightness from the diffused light of 

 the myriads of stars that form it. Most of these stars 

 appear to be extremely small, on account of their enor- 

 mous distances ; and they are so numerous, that, ac- 

 cording to his estimation, no fewer than 50,000 passed 

 through the field of his telescope in the course of one 

 hour in a zone 2 broad. This singular portion of the 

 heavens, constituting part of our firmament, consists of 



