Other springs burst forth at the southern extremity of the plain, close to the defile {62} of Lerna, which, like that of the Erasinus, are supposed to be fed from Lake Stymphalus. Close to them is a chasm filled with water, said to be unfathomable. It abounds in tortoises, and venomous serpents inhabit the adjoining marsh. These are the _kephalaria_, or “heads,” of the ancient hydra of Lerna, which Hercules found it so difficult to seize hold of. Still farther south there is another spring which rises from the bottom of the sea, more than three hundred yards from the shore. This spring—the Doinæ of the ancients, and Anavula of modern Greek mariners—is, in reality, but the mouth of one of the rivers swallowed up by the katavothras of Mantinea. When the sea is still it throws up a jet rising to a height of fifty feet. [Illustration: Fig. 20.—THE PLATEAU OF MANTINEA. From the French Staff Map. Scale 1 : 400,000. K. Katavothras.] Analogous phenomena may be witnessed in the two southern valleys of the peninsula, those of Sparta and Messenia. The Iri, or Eurotas, is, in reality, but a large rivulet, which discharges itself into the Gulf of Marathonisi, at the end of a gorge, {63} through which the waters of the Lake of Sparta forced themselves a passage during some ancient deluge; but it is only on rare occasions that its volume of water is sufficient to remove the bar which obstructs its mouth. The Vasili-Potamo (“royal river”), on the other hand, which bursts forth at the foot of a rock a short distance from the Eurotas, though its whole course does not exceed five miles, discharges a considerable volume of water throughout the year, and its mouth is at all times open. As to the river of Messenia, the ancient Pamisus, now called Pirnatza, it is the only river of Greece, besides the Alpheus, which forms a harbour at its mouth, and it can be ascended by small vessels for a distance of eight miles; but this advantage it owes exclusively to the powerful springs of Hagios Floros, which are fed by the mountains on the east. These springs, which form a large swamp where they rise to the surface, are the real river, if volume of water is to be decisive, and the country watered and fertilised by them was called the “Happy” by the ancients, on account of its fertility. [Illustration: Fig. 21.—BIFURCATION OF THE GASTUNI. From the French Staff Map. Scale 1 : 400,000.]