375 



been placed between the four equinoxial and 

 solstitial signs ; perhaps the number of twenty 

 was derived only from a division of the visible 

 hemisphere into ten parts. It is certain, that 

 this same division engaged the Mexicans to 

 divide the year of three hundred and sixty days 

 into eighteen months ; and that it became the 

 basis of a system, of which we find no vestige in 

 the Old Continent. I am induced however to 

 think, that the division into eighteen months of 

 twenty days is posterior to another into twelve 

 moons of thirty days ; for the method of making 

 a sign of the zodiac preside over each day, and 

 of determining the number of the months by the 

 return of the periodical series, must have been 

 adopted later than the more obvious idea of 

 dividing the year according to the number of 

 lunations it contains. Although the divisions of 

 the ecliptic into twenty-four tsiekis *, and into 

 thirty-six decani, exist in Asia, these divisions 

 have never led to years of ten or fifteen months : 

 and, if antiquity speaks of those of four, six, or 

 twenty-four months, these divisions do not de- 

 pend on the use of periodical series, like the 

 eighteen months of the Mexican year, but on 

 the importance assigned to the equinoxial and 



* Amiot, in les Meraoires concernant lee Cbinois, vol. 2, 

 p. 161. Gaubil, Trait& de l'Astronomie Chinoise, p. 32. 



