elaborated a complicated and remarkably exact system of chronology. They
had determined the length of the year with greater accuracy than the
white invaders; and the different cycles by which they computed time
allowed them to assign dates to occurrences many hundreds of years
anterior.

Although there are local differences, the calendars in use in Central
and Southern Mexico and in Central America were evidently derived from
one and the same original. A great deal has been written upon them, but
for all that many questions about them remain unanswered. We do not know
the Maya method of intercalation; we do not understand the uses of the
shorter Mexican year, of 260 days; we are at a loss to explain the
purpose of doubling the length of certain months, as prevailed among the
Cakchiquels; we are in the dark about the significance of the names of
many days and months; we cannot see why the nations chose to begin the
count of the year at different seasons; and there are ever so many more
knotty problems about this remarkable system and its variations.

What we imperatively need is a supply of authentic aboriginal calendars,
accurately reproduced, for purposes of comparison. Boturini collected a
number of these, which he describes, and long before his day some
specimens had been published by Valades and Gemelli Carreri.[48] They
were, in ancient times, usually depicted by circular drawings, called by
the Spaniards, Wheels (_ruedas_). After the Conquest they were
written out, more in the form of our almanacs. One such, in the Maya
tongue, with a translation, was contributed to Mr. Stephens' _Travels
in Yucatan_, by the eminent Maya scholar, Don Juan Pio Perez.[49]
Several others were in his collection, and are accessible. Dr. Berendt
succeeded in securing _fac similes_ of Kiche and Cakchiquel
calendars, written out in the seventeenth century, and these are now in