III.  After this, while the war was at its height, much alarm was caused by the strange phenomenon seen at the Alban lake, which could not be accounted for on ordinary physical principles.  The season was autumn, and the summer had not been remarkable for rain or for moist winds, so that many of the streams and marshes in Italy were quite dried up, and others held out with difficulty, while the rivers, as is usual in summer, were very low and deeply sunk in their bed.  But the Alban lake, which is self-contained, lying as it does surrounded by fertile hills, began for no reason, except it may be the will of Heaven, to increase in volume and to encroach upon the hillsides near it, until it reached their very tops, rising quietly and without disturbance.  At first the portent only amazed the shepherds and herdsmen of the neighbourhood; but when the lake by the weight of its waters broke through the thin isthmus of land which restrained it, and poured down in a mighty stream through the fertile plains below to the sea, then not only the Romans, but all the people of Italy, thought it a portent of the gravest character.  Much talk about it took place in the camp before Veii, so that the besieged also learned what was happening at the lake.

IV.  As always happens during a long siege, where there are frequent opportunities of intercourse between the two parties, one of the Romans had become intimate with a citizen of Veii, who was learned in legendary lore, and was even thought to have supernatural sources of information.  When this man heard of the overflowing of the lake, his Roman friend observed that he was overjoyed, and laughed at the idea of the siege being successful.  The Roman told him that these were not the only portents which troubled the Romans at the present time, but that there were others stranger than this, about which he should like to consult him, and, if possible, save himself in the common ruin of his country.  The man eagerly attended to his discourse, imagining that he was about to hear some great secrets.  The Roman thus decoyed him away farther and farther from the city gate, when he suddenly seized him and lifted him from the ground.  Being the stronger man, and being assisted by several soldiers from the camp, he overpowered him, and brought him before the generals.  Here the man, seeing that there was no escape, and that no one can resist his destiny, told them of the ancient oracles about his city, how it could not be taken until its enemies drove back the waters of the Alban lake, and prevented its joining the sea.  When the senate heard this they were at a loss what to do, and determined to send an embassy to Delphi to enquire of the God.  The embassy consisted of men of mark and importance, being Licinius Cossus, Valerius Potitus, and Fabius Ambustus.  After a prosperous journey they returned with a response from Apollo, pointing out certain ceremonies which had been neglected in the feast of the Latin games, and bidding them, if possible, force the waters of the Alban lake away from the sea into its ancient course, or, if this could not be done, to divide the stream by canals and watercourses, and so to expend it in the plain.  When the answer was brought back, the priests took the necessary steps about the sacrifices, while the people turned their attention to the diversion of the water.