learn that the Potami, which flows in the depth of the glen below the cave, went in antiquity by the name of the Celadon or ‘Roaring Stream.’ IX. THE PORT OF ATHENS.—Piraeus, the port of Athens, is a rocky peninsula which runs out into the sea in a south-westerly direction for a distance of more than two miles. It is composed of two masses, each over a mile wide, which are united to each other by a somewhat low and narrow ridge or isthmus. The south-western mass, anciently known as the Acte, rises gradually on all sides to a height of nearly two hundred feet. The north-eastern mass attains a height of nearly three hundred feet in the steep rocky hill of Munychia. The ancients believed that the peninsula of Piraeus had formerly been an island, and that it had received its name because it was the land across (_peran_) the water. Modern observation confirms the belief that Piraeus was once an island. The peninsula is joined to the mainland by a stretch of low swampy ground, nowhere more than eight feet above the level of the sea. This stretch of low land, which the ancients called Halipedon, appears to be formed of alluvial soil brought down in the course of ages by the Cephisus, which falls into the sea a little to the east, and which has by its deposits gradually converted the rocky island into a peninsula. Piraeus includes three distinct harbours, each opening to the sea by a separate mouth. These are the great harbour, technically known as Cantharus, on the north-west side of the peninsula, and the two smaller and nearly circular harbours of Zea and Munychia on the south-eastern side. The whole of the peninsula, with its three harbours, was strongly fortified in antiquity. The line of the fortification wall may still be traced almost all round it, and in most places the foundations are so well preserved that it is possible to reconstruct the plan of the fortress as a whole. The wall runs along the shore at such a distance as to be out of reach of the waves, and yet near enough the sea to prevent an enemy from bringing siege engines into play on the beach. It is from ten to twelve feet thick, and is very carefully built of squared blocks of the native limestone without mortar. The quarries in which the stones were hewn may be observed at many points both behind and in front of the wall. In places where the stones have been taken away from the wall to furnish building material for the modern town, we can see the grooves or channels cut in the rock in which the stones were originally bedded. These grooves are each about two and a half feet wide and run parallel to each other, showing that only the outer and inner faces of the wall were of solid masonry, and that the core must have been, as in many ancient Greek walls, filled up with rubble and earth. In the best preserved portions the wall is still standing to a height of five courses or more. It is flanked by towers which project from the curtain at intervals of sixty or seventy yards.