PORTION OF THE COSMOS. SCINTILLATION OF STARS. 69 



accurate catalogues as visible to the naked eye. That the 

 trembling light of the fixed stars distinguishes them from 

 the planets, was early known to the Grecian astronomers ; 

 but Aristotle, in accordance with the emanation and tangen- 

 tial theory of vision to which he adhered, singularly enough 

 ascribed the trembling and twinkling of the fixed stars 

 merely to an effort or straining of the eye. " The fixed 

 stars," said he,( 131 ) "sparkle, but the planets do not : for 

 the planets are near, so that the sight is able to reach them ; 

 but in the fixed stars (irpbg tie TOVQ ^ivovrao) the eye, by 

 reason of the distance and the effort, falls into a tremulous 

 movement." 



In Galileo's time, between 1572 and 1604, in an epoch 

 of great events in cosmical space, and when three new 

 stars( 132 ), brighter than stars of the first magnitude, ap- 

 peared suddenly, and one of them, in Cygnus, continued to 

 shine for twenty -one years, Kepler's attention was parti- 

 cularly drawn to scintillation as the probable criterion of 

 a non-planetary body ; but the state of optics at that period 

 did not permit him to rise above the ordinary ideas of va- 

 pours in motion. ( 133 ) Also, among the newly-appeared 

 stars mentioned in the Chinese annals, according to the 

 great collection of Ma-tuan-lin, the strong degree of scintil- 

 lation is sometimes noticed. 



In and near the tropical zone, from the more uniform 

 character of the atmospheric strata, the comparative or 

 entire absence of scintillation in the fixed stars to within 

 twelve or fifteen degrees of the horizon, gives to the vault 

 of heaven a peculiar character of repose and tranquil bril- 

 liancy. In several of my descriptions of nature, I have 

 spoken of this characteristic of the tropics, which had not 



