Unlike the Book of the Dead, the Book Am Duat is a systematic treatise, which bears the stamp of individual authorship. It is an apocalypse resting on an astronomical foundation, and is, in fact, a minute and detailed account of the passage of the sun-god along the heavenly river Ur-nes during the twelve hours of the night. Each hour is represented by a separate locality in the world of darkness, enclosed within gates, and guarded by fire-breathing serpents and similar monsters. As the bark of the sun-god glides along, the gates are successively opened by the magical power of the words he utters, and their guardians receive him in peace. Immediately he has passed the gates close behind him, and the region he has left is once more enveloped in darkness. But though he is thus able to illuminate for the brief space of an hour the several regions of the other world, it is not as the living sun-god of day that he voyages along the infernal river, but as “the flesh of Ra”—that is to say, as that mortal part of his nature which alone could die and enter the realm of the dead. The river is a duplicate of the Nile, with its strip of bank on either side, its fields and cities, even its nomes, wherein the god, like the Pharaoh, assigns land and duties to his followers. For the followers of Ra have a very different lot before them from that which awaited the followers of Osiris. There was no land of everlasting light and happiness to which they could look forward, nor was their destiny hereafter dependent on their conduct in this life. Their supreme end was to accompany the sun-god in his bark as he passed each night through the twelve regions of the dead, and this could be attained only by a knowledge of the ritual of Am Duat and the mystic formulæ it contained. Few, however, of those who started with the sun-god on his nocturnal voyage remained with him to the last; most of them were stopped in the regions through which he passed, where fields were granted them whose produce they might enjoy, and where each night for a single hour they formed as it were a bodyguard around the god and lived once more in the light. Even the kings of Upper and Lower Egypt were condemned to dwell for ever in this gloomy Hades, along with Osiris and the Khû or luminous souls of an earlier faith. Those who were happy enough by virtue of their knowledge and spells to emerge with Ra into the dawn of a new day, henceforth had their home in the solar bark, and were absorbed into the person of the god.