68 



STATEMENT AND EXPOSITION OF 



of this material similar to that of the Zodiacal Light. It may, however, be asserted 

 that auroral phenomena are most intense in latitude about that of the arctic circle; 

 in which region, it must also be remembered, we have the magnetic poles. It is 

 withal true, that the Zodiacal light seems sometimes to have exhibited (like the 

 Aurora) a ruddy tint. An instance is' mentioned in (91). 



SaturrCs Dtislcy Ring. 



(98) The situation of the dusky ring of Saturn somewhat resembles that of the 

 zodiacal girdle (if supposed to be a terrestrial appendage). But the shape of the 

 dusky ring is diiferent from that of the girdle; and its position, concentric with 

 that of Saturn [7 of (43) and Note], is maintained by the action of many satellites 

 instead of one ; the total action of the several bright rings on particles within 

 being in every case zero. But the dusky ring besides is, as it were, locdled in by 

 the bright rings, which themselves are kept concentric with both the planet and 

 the dusky ring. 



Of the Inclination of the Planes of the Orbits of the Planets and /Satellites to the 

 Equators of their resjpective Primaries; and the relative positions of their Peri- 

 helia and Nodes. 



(99) In a Memoir on the Secular Variations of the Elements of the Orbits of 

 Eight Principal Planets, its author, Mr. John N. Stockwell, M.A., has given us the 

 maximum and minimum inclinations of the planes of those orbits to the invariable 

 plane of the solar system.-^ 



Erom these and the inclination, 7°15', of the plane of the solar equator to the 

 plane of the ecliptic of 1850, as ascertained by Mr. Carrington," we obtain the fol- 

 lowing approximate inclinations of the planes of the orbits to the plane of the sun's 

 equator ; carrying the reference back to that ancient state of things in which the 

 nodes (of the same name), of the sim's equator and those of the planets' orbits in 

 the invariable plane, respectively coincided. 



Inclination of Oebit to Sun's Equatou. 





I Miiiimnm 



Mean 



Maximum 



With . . . 



\ Inclination to 



Inclination to 



Inclination to 





f Inv. Plane. 



Inv. Plane. 



Inv. Plane. 



Mekcbry 



U°56' 



1°18' 



3°31' 



Venus 



5 40 



4 58 



2 24 



Earth 



5 40 



4 37 



2 34 



Mars 



5 40 



2 42 



16 



Jupiter 



5 3(5 



5 2S 



5 11 



Saturn 



4 53 



4 40 



4 39 



Uranus 



4 45 



5 9 



4 33 



Neptune 



5 6 



4 59 



4 53 



Smithsonian Contrihiitiona to Knowledge, vol. xviii, p. 169 of the Memoir in question. 

 As qnotefl in S'r J. Hevschel's Outlines of AMrortonvj (11th edition), (392). 



