20 BUREAU OF AMERICAN ETHNOLOGY [bull. 2S 



of 13 days was interpolated at the end of the xiuhmolpilli, the period 

 of 52 years. Tiiis theory is probably to be ascribed to the learned 

 Jesuit Don Carlos Sigiienza y Gongora, who lived in the second half 

 of the seventeenth century. The Avork of this author, Ciclogratia 

 Mexicana, is apparently lost, but Genielli Carreri and Clavigero refer 

 to it. Sigiienza had important documents at his disposal, papers and 

 picture manuscripts, which belonged to Don Juan de Alva Ixtlilxochitl, 

 a descendant of the roj^al Tetzcocan family, and he was a trained 

 astronomer. His conjecture is all the more acceptable also because it 

 leaves the arrangement of the da3^s in the period of 52 years untouched. 

 In spite of this I think that his assertions rest upon groundless con- 

 jectures. Nowhere in the older authors do we learn that a festival of 

 13 days' duration was held at the end of the period of 52 years. They 

 always refer to one night only, the turning point of the century, dur- 

 ing which the people awaited the flaming up of the new tire upon 

 Uixachtepec with fear and trembling. In the picture manuscripts we 

 find periods of time set down which extend over the period of 52 years, 

 and where the arrangement of the days is carried over without a jump 

 from one period to the other (see, for instance, pages 46 to 50 of the 

 Dresden manuscript, the well-known pages from which E. Forstemann 

 proved the series of dates to be 236, 90, 250, and 8 days apart). On 

 them are recorded, beginning with the day 1 Ahau, the thirteenth of the 

 month Mac, 13 X 2,1>20 days, or a period of 13 X 8, that is, 2 X 52, or 101:, 

 years, in dates separated by regular distances, without a hiatus of any 

 kind between one and the other of the two cycles of 52 years. Still 

 greater periods of time are noted down upon the last leaves of the 

 Dresden manuscript by continuous, uninterrupted dates accompanied 

 by check numbers. 



But the advocates of intercalation also appeal to manuscripts. 

 Clavigero (volume 2, page 62) says: Questi tredici giorni erano 

 gr intercalari, segnati nelle lor dijunture con punti turchini; non gli 

 contavano nel secolo giil compito, neppur nel seguente, ne continu- 

 avano in esse i periodi di giorni, che andavano sempre numerando dal 

 primo sino alio ultimo giorno del secolo ("These thirteen days were 

 the intercalary ones, designated in printing them by blue dots; they 

 were not counted in the century already completed, nor in the follow- 

 ing one either, nor were the periods of days continued in them which 

 were continuously numbered from the first to the last day of the 

 century"). Clavigero himself has not seen these manuscripts, but 

 refers to Don Carlos Sigiienza. The materials which Sigiienza pos- 

 sessed seem for the most part to have passed into the possession of 

 Boturini. In consequence of their seizure by vice-regal authority they 

 disappeared from the scene. A part of them are in the Aubin collec- 

 tion, whose present owner is M Eugene Goupil, of Paris. I do not 

 think that there are any papers among them which justify Clavigero's 



