In the first place, not only are the emissaries subject to a gradual and regular process of change, their passages being slowly clogged and their mouths choked up by the alluvial deposits which in the course of ages raise the bed of the lake; but they are also exposed to sudden and incalculable changes, wrought by earthquakes, landslips, floating logs, and so on, which may in a few minutes either widen the passages or block them up altogether. In the second place, while these changes, whether gradual or sudden, affect the outflow of the water, others not less marked influence its inflow. For the rainfall, on which the inflow ultimately depends, varies not only with the year but with the season. In the sub-tropical climate of the Mediterranean rain hardly falls in summer, and as a consequence the streams in that season either flow with diminished volume or dry up entirely. All these various causes combine to produce secular and periodic as well as irregular and unforeseen variations in the level of lakes like the Copaic mere. In no lake, perhaps, have the annual changes been more regular and marked than in the Copaic; for while in winter it was a reedy mere, the haunt of thousands of wild fowl, in summer it was a more or less marshy plain where cattle browsed and crops were sown and reaped. So well recognised were these vicissitudes of the seasons that places on the bank of the lake such as Orchomenus, Lebadea, and Copae had summer roads and winter roads by which they communicated with each other, the winter roads following the sides of the hills, while the summer roads struck across the plain. With the setting in of the heavy autumn rains in November the lake began to rise and reached its greatest depth in February or March, by which time the mouths of the emissaries were completely submerged and betrayed their existence only by swirls on the surface of the mere. Yet even then the lake presented to the eye anything but an unbroken sheet of water. Viewed from a height such as the acropolis of Orchomenus it appeared as an immense fen, of a vivid green colour, stretching away for miles and miles, overgrown with sedge, reeds, and canes, through which the river Cephisus or Melas might be seen sluggishly oozing, while here and there a gleam of sunlit water, especially towards the north-east corner of the mere, directed the eye to what looked like ponds in the vast green swamp. Bare grey mountains rising on the north and east, and the beautiful wooded slopes of Helicon on the south, bounded the fen. In spring the water began to sink. Isolated brown patches, where no reeds grew, were the first to show as islands in the mere; and as the season advanced they expanded more and more till they met. By the middle of summer great stretches, especially in the middle and at the edges, were bare. In the higher parts the fat alluvial soil left by the retiring waters was sown by the peasants and produced crops of corn, rice, and cotton; while the lower parts,