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-foi’r 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 Memoires concernant les Chinois, vol. 2, 
p. 161. Gaubil, Traits de rAstronomie Cbinoise, p. 32. 
