PORTION OF THE COSMOS. THE PLANETS. 371 



ment of the snowy districts, beiiig a meteorological pheno- 

 menon implying aqueous precipitations dependent, as 

 respects their character, on changes of temperature, and 

 some optical phsenomena presented by the dark spots when 

 the rotation of the planet brings them to the margin of the 

 disk, render the existence of an atmosphere of Mars more 

 than probable. 



The Small Planets. 



In the general considerations ( 603 ) on planetary 

 bodies, we have already designated the group of the small 

 planets (Asteroids, Planetoids, Coplanets, or telescopic or 

 ultra-zodiacal planets) intermediate between Mars and 

 Jupiter as a middle group, forming in some degree a 

 dividing zone, separating the solar domain into an inner 

 and an outer portion the one comprising the four interior 

 planets, Mercury, Yenus, Earth, and Mars; and the other the 

 four exterior planets, Jupiter, Saturn, Uranus, and Neptune. 

 This middle group has a highly distinct character of its own, 

 in the intricate or intersecting, highly inclined, and very 

 excentric orbits of the planets of which it consists; and 

 also in their extraordinary smallness, as the diameter even of 

 Yesta does not appear to equal the fourth part of that of 

 Mercury. When the first volume of Kosmos appeared in 

 Germany in 1845, only 4 of the small planets Ceres, 

 Pallas, Juno, and Yesta, discovered by Piazzi, Olbers, and 

 Harding (1st Jan. 1801 to 29th March, 1807) were 

 known to us. At the present moment (July 1851) the 

 number has increased to 14, being one-third of the number 

 of all the known planetary bodies i. e. 43 primary planets 

 and satellites. 



