122 MEXICO AND CENTRAL AMERICA 
and may be an attempt to determine lucky days for 
planting. 
Bases of Mayan Chronology. Several attempts 
have been made to bring about a concordance of Mayan 
and European chronology with widely varying results. 
Most of these attempts were made by developing a single 
line of evidence and some were based on assumptions 
that can now be disproved. But no single line of evi- 
dence should be deemed sufficient to decide this all im- 
portant question. ‘The general course of Mayan history 
is indicated unmistakably by three principal lines of 
evidence capable of being correlated with each other. 
These are:— 
Ist, Natural developments of sculpture, architecture; 
etc. “> 
2nd, Inscribed dates on monuments. 
3rd, Traditional history in the Books of Chilan Balam. 
A fourth important line of evidence remains to be de- 
veloped in the future. This relates to astronomical 
time. ‘There is more than a suspicion that the Mayas 
were able to predict eclipses and there is a strong possi- 
bility that planetary conjunctions and other calculable 
phenomena were also recorded. Astronomical checks 
on chronology may possibly appear after a careful study 
of the calculations relating to Venus. 
Natural developments in sculpture, etc., validate the 
contemporaneous and therefore historical character of 
many inscribed dates. In fact, the relative chronology 
of the cities of the first great Mayan period, coming over 
600 years, is now upon a very certain basis. After the 
close of this period the dates were no longer inscribed. 
We are still able to indicate the course of change in the 
arts but we cannot express this in terms of vears. Fin- 
ally, in the books of Chilan Balam we have a dependable 
series of traditions affecting a considerable part of the 
VA 
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