ELEMENTS OF ELLIPTICAL MOTION.
1. The mean distance of the planet from the sun, or half the major axis of the orbit.
2. The duration of a mean sidereal revolution of a planet.
3. The mean longitude of the planet at a given epoch.
4. The longitude of the perihelion at a given epoch.
5. The inclination of the orbit to the ecliptic at a given epoch.
6. The longitude of the nodes at a given epoch.
7. The eccentricity of the orbit.
SECULAR VARIATIONS IN ORBIT.
The position of the apsides.
The inclination of the orbit to the ecliptic.
The position of the nodes.
The amount of eccentricity.
NUMBER OF BODIES OF SOLAR SYSTEM.
| Principal planets, including Vulcan, | 9 |
| Asteroids, (1861,) | 71 |
| Satellites, | 18 |
| Periodic comets, | 27 |
| Planetary rings, | 3 |
| Zones of asteroids, probably | 3 |
LAWS OF LIGHT.
| Intensity inversely proportional to the square of the distance from source. | |
| Velocity in miles, per second, | 192,000 |
BODE'S LAW OF PLANETARY DISTANCES.
The intervals between the orbit of Mercury and the other planetary orbits go on doubling as we recede from the sun.
The first of the following series represents the distances from the orbit of Mercury; the second, by adding 4 as the distance of Mercury from the Sun, represents the planetary distances from the centre of the system:—
