PORTION OF THE COSMOS. THE SUN. 869 



times, the Sun's bright image in the sparkling play of the 

 waves of the sea, and in the dew-drops on the blades of 

 grass as the breeze sweeps over the meadow ; the light of 

 heaven, in the various degrees of its intensity and duration, 

 also connects itself by mysterious links with man's inner 

 being, with his intellectual susceptibilities, and with the 

 cheerful and serene, or the melancholy tone of his disposi- 

 tion : " Coeli tristitiam discutit Sol et humani nubila animi 

 serenat." (Plin. Hist. Nat. ii. 6). 



In describing the several cosmical bodies, I commence in 

 each case with the numerical data belonging to them, and 

 place next whatever inferences the present state of our 

 knowledge may enable us to draw respecting their physical 

 constitution. The arrangement of the numerical results is 

 nearly the same as in Hansen's excellent " Uebersicht des 

 Sonnensystems" ( 464 ), but with additions and modifications, 

 inasmuch as, since the year 1837, when Hansen wrote, 

 eleven planets and three satellites have been discovered. 



The mean distance of the centre of the Sun from the 

 Earth is, according to Encke's valuable correction of the 

 Sun's parallax (Abhandl. der Berl. Akad. 1835, S. 309), 

 20682000 (German) geographical miles of 15 to a degree of 

 the terrestrial equator (equal to 82728000 English geogra- 

 phical miles), each German mile containing according to 

 Bessel's examination of ten measured (Kosmos, Bd. i. 

 S. 421, Eng. Ed. p. xlii., Note 130), precisely 3807.23 

 toises, or 22843'33 Paris feet; (in English measure 6086-76 

 British feet to a British geographical mile 60 to a degree.) 



According to Struve's observations of aberration, light 

 takes to reach the Earth from the Sun, or, in other words, to 

 traverse the semi-diameter of the Earth's orbit, 8' 1 7". 7 8 



