The Persians marched into the rocky gorge leading to the temple at Delphi, but just as they were entering the valley a terrible thunderstorm broke forth. The darkness became so great that the soldiers lost their way. The rocks rolled and crashed down upon them; and the soldiers, filled with dread, beat a hasty retreat, and never again dared venture into this valley. In the mean while the Greek fleet at Artemisium had held the Persian vessels at bay, until news was brought of the death of Leonidas, and the passage of Thermopylae. Then the Greeks sailed as fast as they could toward Athens, knowing that they would be needed there to defend the city. The various allies, sure that it would be quite useless to try to defend the northern part of Greece any longer, retreated into the Peloponnesus, and, hoping to prevent the Persians from entering there, hastily began to build a huge wall all across the Isthmus of Corinth, which is only about five miles wide. LII. THE BURNING OF ATHENS. As all their allies were trying only to defend the Peloponnesus, the Athenians were left entirely alone. Many of their friends advised them to abandon their city, and follow the other Greeks southward, leaving all Attica a prey to the foe. This the Athenians did not wish to do, so they sent in haste to Delphi, to inquire of the oracle whether they had better retreat, or attempt to defend their city. As was generally the case, the oracle did not give a plain answer, but merely said, "The wooden walls will defend you and your children." When this answer was brought to Athens, no one could tell exactly what it meant. Some of the citizens fancied that the oracle was advising them to retreat behind the ancient wooden stockade on the Acropolis, but Themistocles insisted that by "wooden walls" the oracle meant their ships. He finally persuaded the Athenians to believe him. All the old men, women, and children were hastily brought on board the ships, and carried to the Peloponnesus, where they were welcomed by their friends. Then the men embarked in their turn, and the fleet sailed off to the Bay of Sal'a-mis, where it awaited a good chance to fight. The Persians swept down into Attica, and entered the deserted city of Athens. Here they gazed in wonder at all they saw, and, after robbing the houses, set fire to the town, and burned down all the most beautiful buildings. The Persians were so delighted at having attained their purpose, and reduced the proud city to ashes, that they sent messengers to bear the glad tidings to the Persian capital. Here the people became almost wild with joy, and the whole city rang with their cries of triumph for many a day. As you will remember, Themistocles had allowed the Spartans to command both the army and the navy. It was therefore a Spartan king, Eu-ry-bi'a-des, who was head of the fleet at Salamis. He was a careful man, and was not at all in favor of attacking the Persians.