112 MEXICO AND CENTRAL AMERICA 



the Supplementary Series. Several of these hiero- 

 glyphs contain the symbol for the moon and the last 

 one contains this symbol with the numerals 9 or 10 to 

 the right or below. It has been suggested that this 

 last glyph stands for a 29 or 30 day month, as the case 

 may be, and that the Supplementary Series records 

 the position of the Initial Series date in a lunar count. 



The Venus Calendar. The Mayan astronomers 

 possessed a remarkable knowledge of the movements of 

 the planets. In particular the apparent revolution of 

 the planet Venus was used as the basis of what we may 

 call the Venus Calendar. The mean synodical year of 

 Venus (nearly 584 days) is divided in the Mayan books 

 into four parts of 236 days (morning star), 90 days 

 (superior conjunction), 250 days (evening star), and 

 8 days (inferior conjunction). These divisions agree 

 closely enough with the actual divisions of the Venus 

 year. But we must remember that the observations 

 were made without instruments, and that the planet 

 cannot be seen by the naked eye when close to the sun. 

 Moreover, we must expect beliefs as to the nature of this 

 planet, personified as a god, to supplement the knowl- 

 edge gained from actual observations. 



The agreement in length between 8 solar years of 

 365 days each and 5 Venus years of 584 days each was 

 recognized and used in ceremonies and calculations. On 

 the five pages of the Dresden Codex, numbered 46-50, 

 are 5 Venus years amounting in all to 2920 days. On 

 page 24 of the same codex (see PI. XXII) we find this 

 sum taken 13 times to make 37,960 days and then 

 this last number taken 4 times to make 151,840 

 days. The number 2920 (5 x 584 and 8 x 365) has a 

 definite relation to the tzolkin or fundamental permuta- 

 tion cycle which results from the following coincidence : 



