ZODIACAL LIGHT. 129 



tail of a comet, whose head was concealed in the vapoury 

 rni.st of the horizon, and which, from its length and appear- 

 ance, presented much similarity to the great comet of 1843. 

 \Ve may conjecture, with much probability, that the remark- 

 able light on the elevated plains of Mexico, seen for forty 

 nights consecutively in 1509, and observed in the eastern 

 horizon rising pyramidally from the earth, was the zodiacal 

 light. I found a notice of this phenomenon in an ancient 

 Aztec MS., the Codex Telleriano-Remensis,* preserved in the 

 Royal Library at Paris. 



This phenomenon, whose primordial antiquity can scarcely 

 be doubted, and which was first noticed in Europe by Childrey 

 and Dominions Cassini, is not the luminous solar atmosphere 

 itself, since this cannot, in accordance with mechanical laws, be 

 more compressed than in the relation of 2 to 3, and consequently 

 cannot be diffused beyond -^ths of Mercury's heliocentric 

 distance. These same laws teach us that the altitude of the 

 extreme boundaries of the atmosphere of a cosmical body 

 above its equator, that is to say, the point at which gravity 

 and centrifugal force are in equilibrium, must be the same as 

 the altitude at which a satellite would rotate round the cen- 



is very obscure in his remarks on comets, observing that their tails are 

 formed " by oblique rays which, falling on different parts of the planet- 

 ary orbs, strike the eye laterally by extraordinary refraction," and that 

 they might be seen morning and evening, " like a long beam,'' when the 

 sun is between the comet and the earth. This passage no more refers 

 to the zodiacal light than those in which Kepler (Epit. Astron. Coper- 

 nicance, t. i. p. 57, and t. ii. p. 893) speaks of the existence of a solar 

 atmosphere (limbus circa solem, coma lucida), which, in eclipses of the 

 sun, prevents it "from being quite night;" and even more uncertain, 

 or indeed erroneous is the assumption that the " trabes quas foicovi; 

 rocant," (Plin., ii. 26 and 27), had reference to the tongue-shaped rising 

 zodiacal light, as Cassini (p. 231, art. xxxi.) and Mairan (p. 15) have 

 maintained. Everywhere amongst the ancients, the trabes are asso 

 ciated with the bolides (ardores et faces), and other fiery meteors, and 

 even with long-barbed comets. (Regarding <W6c, COKIUQ, CoKinir, see 

 Schffer, Sckol. Par. ad Apoll. Mod., 1813, t. ii. p. 206; Pseudo- 

 Aristot., de Mundo, 2, 9 ; Comment. Alex. Joh. Pliilop. et Olymp. in 

 Aristot. Meteor, lib. i., cap. vii. 3, p. 195, Ideler; Seneca, Nat. Qucest., 

 LI.) 



* Humboldt, Mbnumens des Peuples Indigenes de I'Amerique, t. ii. 

 p. 301. The rare manuscript which belonged to the Archbishop of 

 Rheims, Le Tellier, contains various kinds of extracts from an Aztec ritual, 

 on astrological calendar, and historical annals extending from 1 197 to 



K 



