106 ASTRONOMY. 
Velocity and Fall of the Planetary Orbits ; their position with respect to the. 
Sun’s Equator. 
Planets | Mean ee in a | Fall towards the Sun in a |Right Ascension of the #7 
" | Second. ternal Node of the Orit. 
Mercury . ’ | 26.8 Eng miles. | 8.46 316° 51’ 
Venus | 19.6 | 2.42 | 242 45/ 
Earth . 16.4 | 1.2% | 248 0! 
Mars . | 13.6 | 0.55 i, | 2o4 Goa, 
Vesta . er | gous | 0.20 | 180° 33’ 
Juno gaa: 2 10.4 | 0.20 | 197 a 
Ceres” One 2 | 10.0 | 0.20 | 208 43’ 
Pallas . ¥ 10.0 0.20 182 19 
Jupiter: ) «say es. ox | 6.8 0.047 242 Hl 
Saturn Be | 52 0.014 2 931 12! 
Urantes at go| aa 48 0.003 247 30! 
Neptune . | 2.8 
Inclination and Motion of the Planetary Orbits. 
Planets | Inclination of the Orbit to Arce of the Retrograde Duration of the Retrograde 
the Sun’s Equator. Motion. Motion 
| : ¢ 
Mercury . | 2° 54’ 8°33’ 16°18’ | 20 and 24 days. 
Venus. 4° °9 15 20 To al. | 4t) “ Aaa oe 
Earth . | 7 30 
Sar ee, : 5 50 ll 8 19 30 G2)" Sra 
Vestas ee ee 4 28 
Juno . 16 28 | 
Ceres . | 3. 43 
Pallas . to hae 7 eg 
Jupher, 1 ow 8 10 0 | 119°" 
Saturn : | ‘Salma Yl 6 48 ane 
Uranus PO a | 3 36 ey Ai 
ee —————————~ — 
The most important items respecting the moons of Jupiter, Saturn, and 
Uranus, will be found further on, principally in section 38. Sections 30 
and 31 will contain the principal points in the history of our moon. 
Annual Revolution of the Earth around the Sun, and Various Phenomena 
resulting from this Revolution. 
26. The central figure on pl. 8 is intended to exhibit clearly, with many 
other phenomena, the annual revolution of the earth about the sun; never- 
theless, for the better knowledge of the whole subject, it will be necessary 
to premise a few general observations. It is, in the first place, evident 
that bodies cannot themselves change their condition, and that thus a body 
once set in motion can never stop—that it will continue to move in the 
same direction and with the same velocity as when it-set out, unless some 
other external force changes its direction or velocity. This peculiarity of 
106 
