In building the great walls, Neptune was assisted by Apollo, who had also been driven from Olympus for an offense against Jupiter. Apollo had a son named Æs-cu-laʹpi-us, who was so skilled a physician that he could, and did, raise people from death to life. Jupiter was very angry at this. He feared that men might forget him and worship Æsculapius. He therefore hurled a thunderbolt at the great physician and killed him. Enraged at the death of his son, Apollo threatened to destroy the Cyclops, the giant workmen of Vulcan, who had forged the terrible thunderbolt. Before he could carry out his threat, however, Jupiter expelled him from heaven. He remained on earth for several years, after which he was permitted to return to his place among the gods on the top of Mount Olympus. [Illustration: NEPTUNE. _National Museum, Athens._] Though Neptune was bound to serve Laomedon for one year, there was an agreement between them that the god should get a certain reward for building the walls. But when the work was finished the Trojan king refused to keep his part of the bargain. Apollo had assisted by his powers of music. He played such tunes that he charmed even the huge blocks of stone, so that they moved themselves into their proper places, after Neptune had wrenched them from the mountain sides and had hewn them into shape. Moreover, Apollo had taken care of Laomedon's numerous flocks on Mount Ida. During the siege, Neptune, in a conversation with Apollo before the walls of Troy, spoke of their labors in the service of the Trojan king: "Hast thou forgot, how, at the monarch's prayer, We shared the lengthen'd labors of a year? Troy walls I raised (for such were Jove's commands), And yon proud bulwarks grew beneath my hands: Thy task it was to feed the bellowing droves Along fair Ida's vales and pendant groves." POPE, _Iliad_, Book XXI. Long before this, however, the two gods had punished Laomedon very severely for breaking his promise. Apollo, after being restored to heaven, sent a plague upon the city of Troy, and Neptune sent up from the sea an enormous serpent which killed many of the people. A great serpent from the deep, Lifting his horrible head above their homes, Devoured the children. LEWIS MORRIS. In this terrible calamity the king asked an oracle in what way the anger of the two gods might be appeased. The answer of the oracle was that a Trojan maiden must each year be given to the monster to be devoured. Every year, therefore, a young girl, chosen by lot, was taken down to the seashore and chained to a rock to become the prey of the serpent. And every year the monster came and swallowed up a Trojan maiden, and then went away and troubled the city no more until the following year, when he returned for another victim. At last the lot fell on He-siʹo-ne, the daughter of the king. Deep was Laomedon's grief at the thought of the awful fate to which his child was thus doomed.