338 SPECIAL RESULTS IN THE UEANOLOGICAL 



light of the Sun is nearly 7 times more intense at the sur- 

 face of Mercury than on that of the Earth, it must be 368 

 times less intense on Uranus. The ratio of warmth is not 

 here considered, because it is a complicated phenomenon de- 

 pending on the existence or non-existence of planetary atmo- 

 spheres, their heights, and special constitution. I will merely 

 allude to the conjecture of Sir John Herschel respecting the 

 temperature at the surface of the moon, " which," he thinks, 

 " may perhaps considerably exceed that of the boiling-point 

 of water" ( 539 ). 



)3. Satellites. 



General comparative considerations respecting subordinate 

 planets or satellites have been already given with some de- 

 gree of fulness in the "Picture of Nature" in the 1st 

 volume of Kosmos (S. 99 104, German; p. 86 91, Eng- 

 lish). At that time (March 1845) only 11 planets and 18 

 satellites were known. Of asteroids also called telescopic 

 or small planets only four had been discovered viz. 

 Ceres, Pallas, Juno, and Yesta. At the present moment 

 (August 1851) the number of primary planets exceeds that 

 of secondary planets or satellites ; for we now know 22 of 

 the former, and 21 of the latter. After a thirty-eight years' 

 interruption of planetary discoveries, from 1807 to De- 

 cember 1845, the discovery of Astrsea by Hencke was the 

 first of a long succession by which 10 new small planets 

 have become known to us. Of these, Hencke at Driesen 

 recognised two (Astraea and Hebe) ; Hind, in London, four 

 (Iris, Flora, Victoria, and Irene) ; Graham, at Markree 

 Castle, one (Metis) ; and De Gasparis, at Naples, three (Hy- 

 geia, Parthenope, and Egeria). The recognition of the 



