506 COSMOS. 



{asteroids, planetoids , co- planets, telescopic or ultra-zodiacal 

 planets] under the name of an intermediate group, which, to 

 a certain extent, forms a zone of separation between the 4 

 interior planets (Mercury, Venus, the Earth, and Mars), and 

 the 4 exterior planets of our solar system (Jupiter, Saturn, 

 Uranus, and Neptune). Their most distinctive features con- 

 sist in their interlaced, greatly inclined, and extremely 

 excentric orbits; their extraordinary smallness, as the diameter 

 of Vesta does not appear to equal even the fourth part of the 

 diameter of Mercury. When the first volume of the Cosmos 

 appeared (1845), only 4 of the small planets were known: 

 Ceres, Pallas, Juno, and Vesta, discovered by Piazzi, Olbers, 

 jmd Harding (between January 1, 1801, and March 29, 1807); 

 at the present time (July, 1851), the number of the small 

 planets has already increased to 14; they form numerically the 

 third part of all the 43 known planetary bodies, '. e. of all 

 principal and secondary planets. 



Although the attention of astronomers was long directed 

 in the solar regions to increasing the number of the members 

 of partial systems the Moons which revolve round principal 

 planets and to the planets to be discovered in the furthest 

 regions beyond Saturn and Uranus ; now since the acci- 

 dental discovery of Ceres by Piazzi, and especially since the 

 foreseen discovery of Astrea by Encke, as well as the great 

 improvements in the star- charts 60 (those of the Berlin Academy 

 contain all stars as far as the 9th, and partly to the 10th 

 magnitudes), a nearer space presents to us the richest, and 

 perhaps inexhaustible field for astronomical industry. It is 

 an especial merit of the Astronomische Jahrbitch, which is 

 published in my native town by Encke, the Director oi the 



80 With regard to the influence of improved star-charts 

 \ipin the discovery of the small planets, see Cosmos, vol. iii. 

 pp. 155 and 156. 



