MORLEY— MAYA SUPPLEMENTARY SERIES 



Although final answer to this question must necessarily await the 

 complete decipherment of the series, it is already possible to forecast 

 with some little assurance the probable nature of the count. The Sup- 

 plementary Series probably fix the accompanying Initial Series dates 

 in a lunar calendar, which differed in each city. 



They appear to declare the kind of lunar month, i.e., whether of 

 29 or 30 days in length, in which the accompanying Initial Series 

 dates fall (Glyph A) ; and they probably fix these current lunar 

 months in a lunar calendar composed of a series of groups, containing 

 5 or 6 lunations each (Glyphs C, D, and E). Other astronomical phe- 

 nomena actually or ceremonially important on the accompanying 

 Initial Series dates may also be recorded (Glyph X). 



The underlying purpose of the series would appear to have been 

 the attempt to arrange a series of 29- and 30-day lunar months in 

 such a way as to keep the resultant lunar calendar as close as possible 

 to the actual time of the lunar revolutions. As already pointed out, 

 PP- 5 I- 58 of the Dresden Codex achieve this difficult feat for a period 

 of more than 32 years without the cumulative error reaching a whole 

 day at any point in the entire series of 405 lunations. 



It is obvious that a straight alternating sequence of 29- and 30-day 

 months will run ahead of the actual lunar revolutions at a rate of 

 .03 of a day every lunation. This is due to the fact that the period 

 of a lunar revolution is .03+ of a day in excess of 29J/2 days, i.e., 

 29.530588, and the cumulative error in such an arrangement would 

 exceed a day in less than three years. 



We may feel perfectly confident, even if we did not have the direct 

 evidence of the Dresden Codex to the contrary, that the old Maya 

 astronomer priests never fell into such a capital blunder as this. 

 They doubtless recognized very early in their cultural history that it 

 was necessary to interpolate an extra 30-day month every once in a 

 while in order to keep their lunar calendar in harmony with the true 

 lunar revolutions; and that such interpolations of 30-day months 

 were actually made is amply proved by the passage in the Dresden 

 Codex already cited. Of the 405 lunar months there recorded, 214 

 are composed of 30 days each, and 191 of 29 days each; and the total 

 number of days in the entire period falls less than a day behind 405 

 lunations: 



214 X 30 = 6420 days. 405 X 29.53059- = 1 1959.8889- 

 191 X 29 = 5539 days. 



405 lunar 



months = 1 1959 days. 405 lunations = 11959.89 days. 



[39i] 



