A quasi-nine year oscillation of the water level in Lake Copais (Greece) cited by Theophrastus (4th Century B.C.) and Pliny (1st Century A.D.)

摘要

From the analysis of the modern rainfall data in the area of Lake Copais in Beotia of eastern Greece and on the basis of the observations of the water level quoted by Theophrastus (4th century B.C.) from earlier days than his own, as well as by Pliny (1st Century A.D.), it seems that a quasi-nine year oscillation becomes prevalent from time to time in the rainfall of the general area of this lake though we do not know the physical cause of the phenomenon.