Jaeigo 災異考 includes portent records for 841 days, from the second month, 1624 to the ninth month, 1655. The records are divided into the following two types: portent records from Gwansanggam 觀象監 and those from local government offices. While the movements of the moon and the stars appeared most frequently among Gwansanggam portent records, natural disasters and abnormal weather received the highest attention among the local portent records.
In addition to the natural phenomena, Jaeigo also includes 16 entries about human affairs. They are particularly noteworthy because most of these records are related to the national crises in the seventeenth century. For example, the first article in Jaeigo is about Yi Gwal’s 李适 Rebellion. We can also find many entries relating to the First Manchu Invasion of Korea in 1627. The arrangement of years in King Injo 仁祖 period is also notable, because this reveals that Jaeigo was not simply a record of natural phenomena but that of portents that were in association with human affairs.
Due to the intentional editing of the records about the movement of the moon and the stars, the quantity of these records increased. The reason why the author of Jaeigo emphasized them was its astrological meaning, signifying rebellions, wars, and famines.
Although the circumstances surrounding the compilation of Jaeigo are not clear, there are some plausible guesses. The entry of the ninth month, 27th day, 1655 is the last record in Jaeigo. From this, we can surmise that Jaeigo was compiled in the early tenth month, that year. As for the compilers of Jaeigo, there are several possibilities. It might be compiled by Gwansanggam or by individual literati. It is also possible that King Hyojong 孝宗 could have ordered to compile Jaeigo. Lastly, Jaeigo might be compiled in order to urge the king’s moral reflection. It is because kings were considered to be responsible for the portents.