an extensive lake in Northern Bocotia, so called from the town of Copais, at its northern extremity. This lake is mentioned in the ancient classics under many names. By Homer it is called Cephissus, from the name of the river Cephissus, which falls into it; while by other writers it is called Onchestus, Orchomenos, Hallartus, &c., from the towns of those names on its shores. The waters of the lake are deepest at its northern extremity, on which Copais stands, and since they were never dried up there in the hottest summer, as they generally were in the neighbourhood of the other towns, the title Copais was gradually recognised as the most appropriate. The lake itself was formed by the waters of the Cephissus, which, instead of flowing into the sea by an open channel, spreads itself over an extensive tract of low-lying country, surrounded on every side by lofty mountains. Four principal catavothra serve to draw off the superfluous waters of the Copais into the sea; but as these were found to be sometimes insufficient, two great artificial tunnels were constructed at a very early period at the depth of more than 100 feet below the ground, and with shafts let down into them at regular distances. By means of these tunnels the bottom of the lake was originally kept dry, and either served as pasture ground for immense herds of cattle, or yielded valuable corn crops to the inhabitants of the cities on its banks. In course of time the tunnels were choked up, and though attempts were made by Alexander the Great to clear them out, they were never again rendered fully serviceable. In consequence of this neglect, the waters of the river were gradually allowed to accumulate, and now form, according to the description of Colonel Mure, "a large yellow swamp, overgrown with sedges and reeds and canes, through which the river may be distinguished oozing its sluggish path for several miles. Even where the course of the stream could no longer be traced in one uninterrupted line, the partial openings among the reeds in the distance appeared but a continuation of its windings. Nor is the transition from dry land to water in any place distinctly perceptible; the only visible line of boundary between them, unless where the mountains stretch down to the shore, is the encroachment of the reeds on the arable soil, or the absence of the villages with which the terra firma is here studded in greater numbers than usual."