The basin of the Cephissus, enclosed by the chains of the Œta and Parnassus, is one of the most remarkable from an hydrological point of view. The river first flows through a bottom-land formerly a lake, and then, forcing for itself a passage through a narrow defile commanded by the spurs of Mount Parnassus, it winds round the rock upon which stood the ancient city of Orchomenus, and enters upon a vast plain, where swamps and lakes are embedded amidst cultivated fields and reed-banks. These swamps are fed, likewise, by numerous torrents descending from the Helicon and other mountains in its vicinity. One of these is the torrent of Livadia, into which the bounteous springs of Memory and Oblivion—Mnemosyne and Lethe—discharge themselves. In summer a large portion of the plain is dry, and it yields a bountiful harvest of maize, the stalks of which are sweet like sugar-cane. But after the heavy rains of autumn and winter the waters rise twenty, and even twenty-five feet, and the plain is converted into a vast lake, ninety-six square miles in extent. The myth of the deluge of Ogyges almost leads us to believe that the rising floods occasionally invaded every valley which debouches into this basin. To the ancients the shallower part of this lake was known as Cephissus, and its deep eastern portion as Copais, from Copæ, a town occupying a promontory on its northern shore, and now called Topolias. [Illustration: Fig. 14.—LAKE COPAIS From the French Staff Map. Scale 1 : 500,000. K. Katavothras.]