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history and chronology of their ancestors. These 

 manuscripts, which contain a great number of 

 dates, reckoning at the same time according to 

 the Christian era, and according to the civil and 

 ritual calendar of the natives, have been studied 

 with advantage by the learned Carlos de Siguen- 

 za, professor of mathematics at the university 

 of Mexico ; by the Milanese traveller, Boturini 

 Benaducei; by the Abbe Clavigero; and latterly 

 by Mr. Gama, whose astronomical labours I 

 have had occasion to mention in another work *. 

 Finally, in 1790, a stone of enormous bulk, 

 covered with characters evidently relative to the 

 Mexican calendar, the religious festivals, and 

 the days in which the Sun passes the zenith of 

 the city of Mexico, was discovered in the founda- 

 tions of the ancient teocalli. This served at the 

 same time to clear up some doubtful points, and 

 call the attention of some enlightened natives to 

 the Mexican calendar. 



I endeavoured, not only during my stay in 

 America, but after my return to Europe, to study 

 carefully every thing that has been published 

 on the division of time, and the mode of inter- 

 calation among the Aztecks. I examined on 

 the spot the celebrated stone found in the Plaza 

 Mayor, and represented in the twenty-third 



* Essai polit. sur le 3\lexique, vol. 2, p, 24, de 1 'edition 

 in 8vo. 



