Thus Ptah was one of the forms under which the Egyptians invoked the creator, the highest god. On a pillar of Memphis, now in the Berlin Museum, belonging to the time of the nineteenth dynasty, he is called "the only unbegotten begetter in the heaven and on the earth," "the god who made himself to be god, who exists by himself, the double being, the begetter of the first beginning." Other inscriptions and records denote him as "the creator in heaven and on earth, who has made all things, the lord of all that is, and is not."[35] Below Memphis lay On, the city of the sun (Heliopolis). Here the spirit of the sun, Ra, was the pre-eminent god. In Manetho's list Ra succeeds Ptah in the kingdom. "The Egyptians," says Plutarch, "regard the sun as the body of the beneficent power, the visible form of a being only comprehensible to thought. The morning sun they represented as a new-born child seated on a lotus leaf, and thrice each day--at sunrise, noon, and sunset--they offered incense to Helius."[36] We also find that the Egyptians represented the sun of the winter months as a little child, the sun of the vernal equinox as a youth, that of the summer solstice as a bearded man, and again, the sun of the autumnal equinox as an old man.[37] Hence they looked at the yearly course of the sun under the allegory of human life. Plutarch's remark about the morning sun shows that they regarded the daily course of the sun from the same point of view, and when he tells us that according to Egyptian story, Apopis made war against the god of the sky,[38] his statements are confirmed by the monuments. According to the inscriptions Ra is "revealed in the abyss of the sky," he is throned "in the orb of the sun," "he moves his egg." "A Supplication to Ra"--such are the words of a prayer--"who each day by himself brings himself to a new birth. Ra has created all that is in the abysses of the sky."[39] In the tombs of the Ramesids, at Thebes, the course of the sun is represented by the hour of the day and night. On the form of the blue outstretched goddess of the sky appears the boat of the sun, for the Egyptians conceived the sun as navigating the air in a skiff, as they navigated the Nile; and in the boat is Ra, a child with finger in mouth at the first hour of the morning. As the day goes on the child increases in size, and at every hour the spirits who lead the boat are changed. In the hours of the afternoon the evil serpent, Apep, the darkness, the Apopis of Plutarch, attempts to swallow the sun, but twelve spirits draw the serpent by ropes to the side. In the hours of the night the sun-god is inclosed in his shrine on the boat, which is carried along by spirits changing every hour over the waters of the under world to the east--just as the boats on the Nile are drawn against the stream--so that he may again shine out in the east on the next morning. The hieroglyphics accompanying the navigation of the night