MARS PLANETOIDS JUPITER SATURN URANUS NEPT UNE. 



CHAPTER IV. 



MARS PLANETOIDS JUPITER SATURN URANUS NEPTUNE. 



XTERIOR to our terrestrial world in the system, its noblest com 

 peers are to be found, whether we consider the magnitude of 

 their forms, the peculiarities of their structure, or the number 

 of their attendants. The planets technically called superior 

 are known to lie out in space beyond the orbit of the earth. 

 This is shown by several decisive proofs. They never appear 

 crescent-shaped like Mercury and Venus, or exhibit any 

 perceptible phase when viewed through a telescope, but are 

 always seen with a full orb, with the exception of Mars, whose 

 appearance is often gibbous. Jupiter, Saturn, and Uranus 

 always appear round, and the gibbosity of Mars is but a slight deviation from a circle. The 

 inference is, that we see these planets in nearly the same direction in which the sun's rays 

 enlighten them, and consequently the position of the earth must be comparatively proximate 

 to the centre of their orbits. They are also never observed, when in the direction of the 

 sun, to transit his disk, which would occasionally occur, if their path was interior to that 

 of the earth, and carried them between us and the luminary. They are likewise seen at 

 all distances from the sun, even in opposition, or in that quarter of the heavens which is 

 diametrically opposite to the sun's place, rising in the east at sunset in the west, and 

 being visible at midnight, which would plainly be impossible if the earth's orbit circum 

 scribed theirs. These facts prove their position in the system to be exterior to our own. 

 The external planets are chiefly distinguished from the internal by the attendance of 

 secondary bodies, supplying in some degree to their primaries the place of the sun in his 

 absence, and compensating for that diminution of his light when present, which arises 

 from their vast distance from him. Mercury and Venus appear to have no moon, for, 

 in connection with the earth, they answer the purpose of satellites to each other, Venus 

 shining with great splendour in the night of Mercury, and our own globe forming a bril 

 liant object in the night of Venus. At that point of the system in which we are placed, 

 the scheme of satellites seems to commence, and with the exception of Mars and the 

 asteroids it is a feature belonging to the other planets. If a moon should ever be dis 

 covered revolving around Mars, the law of secondary bodies attending the outlying 

 planets would be unbroken from the point we occupy in the system to its outskirts, for 

 the case of the asteroids may be excluded, their whole character being anomalous. Even 

 as it is, the rule is general exterior to the earth's path ; and there may be peculiar 

 circumstances, not yet known, to explain the exceptive case of Mars. The number of 

 secondary bodies appears to be proportioned to the wants of the primaries. While our 

 globe has one, Jupiter, at five times the distance from the sun, has four ; Saturn, at 

 nearly ten times the distance, has eight, besides the enormous rings, which afford an 

 illumination equal to several thousand such attendants ; and Uranus, of nearly twice the 

 distance of Saturn, besides his discovered five or six, may have hundreds that escape our 

 notice, owing to the immense interval that separates him from us. 



MARS, the nearest to us of the exterior planets, was, in former ages of superstition, 

 the dread of the terrestrials on account of his fiery aspect, and ministered more than any 

 other celestial object to give employment to the astrologers, and to fill their coffers : 



