104 MEXICO AND CENTRAL AMERICA 
was only eighteen times the preceding one instead of 
twenty times, or 360 instead of 400. The 360 was prob- 
ably adopted because it comes within five days of the 
length of the year. After this change the ascending val- 
ues are 1, 20, 360, 7,200, and 144,000. A Mayan number 
can be written conveniently in imitation of our own 
system by marking dashes between the “‘positions’’ or 
periods. ‘The long number that is set down as follows 
9-12-16-7-8, equals:— 
9x 144000 1,296,000 
12x 7200 86,400 
16 x 360 5,760 
7x 20 140 
8 x 2 8 
1,388,308 
days in the decimal system. In speaking of such a num- 
ber, however, names would be applied to the periods, 
thus :— 
Cycle 144000 days 
Katun 7200 days 
Tun 360 days 
Uinal 20 days 
Kin 1 ‘day 
The number given above would be read 9 cycles, 12 
katuns, 16 tuns, 7 uinals, and 8 kins. It is convenient 
to remember that a tun is a little less than a year, a 
katun, a little less than twenty years, and a cycle a little 
less than four hundred years. 
The True Year. So far we have been concerned 
primarily with the counting of days—the astronomical 
time unit determined by the revolution of the earth up- 
on its axis. Now, although the day is not contained 
evenly in the other astronomical time periods (the 
month, the year, and the apparent revolutions of the 
planets) the Mayan scholars made some remarkable 
correlations of the heterogeneous data. 
