251 
in diameter^ four centimetres high, and three 
millimetres thick. We can scarcely conceive 
how a vitreous and fragile substance could be re- 
duced to the state of so thin a plate. Besides, 
texpatl differs from obsidian, a substance which 
the Mexicans called iztli; jade, hornstone, and 
flint being confounded under the denomination 
of tecpatl. 
The sign ollin or ollin-tonatiuh^ presides, in 
the beginning of the cycle of 52 years, over the 
seventeenth day of the first month. The expla- 
nation of this sign has greatly embarrassed the 
Spanish monks, who, without the slightest ele- 
mentary notions of astronomy, attempted to ex- 
plain the Mexican calendar. The Indian authors 
translate ollin by motions of the Sun, When 
they find the number nahui added, they render 
nahui ollin by the words Sun (tonatiuh) in his 
Jour motions ; sometimes (Plate 37) like two 
ribands intertwined, or rather like two portions 
of curves, which cross each other, and which 
have three perceptible inflections at their sum- 
mits ; sometimes (Plate 23) like the solar disk 
surrounded with four squares, which contain the 
hieroglyphics of the numbers one fee) and four 
{nahui) ; at other times like three prints of feet. 
The four squares allude, as we shall soon explain, , 
to the famous tradition of the four ages, or four 
destructions of the world, which took place on 
the days 4 tyger^ nahui ocelotl ; 4 wind, nahui 
