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Cincinnati Society of Natural History. 



ian, and passing through the zenith. The coincidence of the shadows of 

 the two threads would make known the day when the sun was in the ze- 

 nith, in going from the equinoctial to the Tropic of Cancer, and again, 

 when the sun returned to the equinoctial ; for in those two days the 

 shadow of the upper thread would exactly coincide with that of the lower, 

 precisely at the moment of mid-day. This occurs on the 16th or 17th of 

 May (the day Naui OcelotV) when the sun passes first through the zenith, 

 and the second time, 26th or 27th of July, (the day 10- Cohuatl.) 



By means of the shadow of the upper thread, P, P, they knew exactly 

 the day of the " Trecena," which was dedicated to the sun, on which oc- 

 casion they celebrated grand festivals, which were left to the charge of the 

 priest or principal minister [Up cou qua cuilt ziii), the master of cere- 

 monies. They well knew that at the end of one of their cycles of fifty-two 

 years the civil year had receded thirteen days, and in order to equalize it 

 to the solar year, they intercalated those days. It was easy for them to 

 ascertain, in any year, how many of these thirteen days they must take 

 into their reckoning, in order to verify the precise time of the equinoxes, 

 and solstices, and transits of the sun through the zenith. 



This stone also served as a solar dial, and in addition to its marking 

 noon by the vertical and parallel shadows cast by the gnomons, X and Z, 

 they also pointed out the hours of nine in the morning and of three in 

 the afternoon ; times which they particularly observed for their rites and 

 ceremonials. The hour of nine was marked by the shadows of the gnomon 

 Z when it passed along the lelt edge "z " of the frame of the " Ocelotl," 

 and through the middle of the circlet "g" in the circle of the sun, and 

 along the right side " s" of the frame of Quiahuitl, and coinciding with 

 the lower gnomon S. In the like manner the shadow passing along the 

 right side of the frame of Ehecatl at " s," and through the circlet " y," 

 and through the left side at " h " of the frame which includes the 

 symbol "Atl," and thence continued through gnomon Y, in the lower part of 

 stone, this shadow would point out the hour of three in the afternoon. 



The Mexicans also took account of the times of the night, especially of 

 the hours of nine in the evening and three in the morning ; which hours 

 they knew from the rising and culmination of certain stars, according to 

 the time of the year, as is ascertained from what has been stated by both 

 Torquemada and D. Hernandez. They expressly state the hours in which 

 incense was daily burned to the sun, and sacrifices offered up. 



This stone was destined for other purposes, in addition to those which 

 we have stated, but as little has been narrated on these matters in the his- 

 tories, we could not find out very much about them. It has been ascer- 



