The reason for the decline of the early Maya civilization is rather obscure. A glance at the scheme of dating will show how closely the last dates at each of the ruined sites correspond one with another. It does not of course follow that the cessation of initial dates implies the abandonment of the “cities,” for they may have been centres of religious life for years later; indeed Cichen was visited as a sacred place until Spanish times, and the Lacandons of to-day still make offerings in the deserted temples. But the abrupt termination of the dating system at least implies some important change, and it may be that about the beginning of the tenth cycle the “long count” was abandoned in favour of the “katun count” as exemplified in the books of Chilan Balam. In any case none of the buildings show evident signs of forcible destruction, and no traces of a military invasion of Maya territory appear. The instability of Central American political organizations is very marked; there was a strong tendency for a state, composed originally of independent self-contained pueblos, to split up into smaller elements under the slightest pressure applied from within or without. The Maya, to judge from the monuments, had enjoyed centuries of peace, and only in the north-east and north do we find reliefs which give any hint of war. But these may be significant, and no doubt the decline of the old culture was due to pressure exercised by their northern neighbours, a pressure which had its origin in the steady southerly drift of tribes from regions considerably further north, and which led to the occupation of the Mexican valley by the Nahua-speaking Toltec.