APPENDIX. 



Resemblances and Differences of Saturn and the Earth (the 

 minor Saturn). 



1. Abnormal Density ; Earth's too great for the region, Saturn's 

 too small The former took its large density from extra-equatorial 

 parts of the sun's atmosphere ; latter from material abstracted 

 from Uranus. 



2. Great oblateness in the nebulous state of former time, shown 

 by the great distance of satellites in both cases. 



3. Each has more satellites than any other planet in the same 

 region. 



4. Saturn's satellites were formed before his rings, and so kept 

 the latter in place. The earth's moon and the girdle agree nearly 

 in their principal planes and orbit with the plane of the ecliptic; 

 and were, therefore, probably established before the earth's axis 

 got its inclined position. 



In completing my account of the zodiacal light, I will tran- 

 scribe here further details of the agreement of my hypothesis 

 with observed phenomena. 



Case 1. The zodiacal light appears narrow and tapering just 

 about the time of the new moon, as though the sun^s light were 

 indeed transmitted at that time through the least curved, and 

 probably somewhat rarer, sides of the oval-shaped girdle, and 

 that for a great part of the length of the oval. 



Case 2. After the new moon, and when the moon is approach- 

 ing her first quarter ; when the moon has set, and the twilight 

 has disappeared, the zodiacal light does not extend so high as in 

 the preceding case, its termination is broader, and not so sharply 

 curved, and the intensity of the light, withal, is not especially 

 conspicuous ; as though the sun^s light, in all its transmission, 

 passed through the rather less dense portion, of the girdle, and 

 passed out of it in a direction more across the same (as in the 

 Fig.), and not so nearly at a tangent to it, as under the circum- 

 stances indicated in the preceding case. 



Case 3. After the Full Moon, and when the moon is approach- 

 ing her Last Quarter ; then before the rising of the moon, and 

 after the end of twilight, a luminous spot of a considerable size, 



(28) 



