﻿The Aztec Calendar Stone. 



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what similar to this one, but representing the other half of the ecliptic, is 

 yet to be found. 



There are certain holes near the edges of the outer cylinder of the Cal- 

 endar Stone. These holes are drilled so as to be perpendicular to the face 

 of the stone, and are designated by the letters X, Z, and S, V, P, P, and 

 Q, Q, which correspond nearly with the subdivisions of the circle into 

 eight parts, designated by the letters L, L. 



The stone was placed in a vertical position, parallel to the prime vertical 

 plane (i. e., due east and west), and facing to the south, and Gama states 

 that they fixed two gnomons of equal length into the holes, X and Z ; also 

 two of equal length, but longer than the first two, at S and Y; the differ- 

 ence in the two sets of gnomons was made equal to that which exists be- 

 tween the zenith of Mexico and the Tropic of Cancer. Threads or fine cords 

 were stretched through the ends of each set of gnomons, hence, the shadow of 

 the upper thread (on the day of "ce Ozomatli " in the year 13 Acatl), or 

 on the 22d of June. When the sun attains its highest declination, the shad- 

 ows of these threads will coincide in a due east and west line upon the face 

 of a horizontal plane, and the angle formed by a plane containing the 

 threads, with the equatorial plane minus the angle P E Z, will give an angle 

 equal to the latitude of Mexico. (Fig. 1.) 



Figure i. — Diagram showing sun in the zenith on May 17th and July 27th. 



Or, the gnomons may have been arranged of such relative lengths, that, 

 at the equinoxes, the plane of their shadows would coincide with the 

 equatorial plane, and then the angle made with the face of the Calendar 

 Stone (i. e., Q E Z), would give the latitude of Mexico. 



The other four holes, equally distant, are P, P, and Q, Q, which answer 

 the purpose of holding four gnomons of equal length; through the ends of 

 each pair threads were stretched horizontally, the thread P, P, over the 

 thread Q, Q, and in the same vertical plane, at right angles to the merid- 



