The first of these is the _De rerum natura_, written to enlighten his king, Sisebut, “on the scheme (_ratio_) of the days and months, the bounds of the year and the change of seasons, the nature of the elements, the courses of the sun and moon and stars, and the signs of tempests and winds, the position of the earth, and the ebb and flow of the sea.” Of all of which, continues Isidore, “we have made brief note, from the writings of the ancients (_veteribus viris_), and especially those who were of the Catholic Faith. For it is not a vain knowledge (_superstitiosa scientia_) to know the nature of these things, if we consider them according to sound and sober teaching.”[128] So Isidore compiles a book of secular physical knowledge, the substance of which is taken from the _Hexaemeron_ of Ambrose and the works of other Fathers, and also from the lost _Prata_ of pagan Suetonius.[129] Of course Isidore busied himself also with history. He made a dismal universal _Chronicon_, and perhaps a History of the Kings of the Goths, through which stirs a breath of national pride; and after the model of Jerome, he wrote a _De viris illustribus_, concerned with some fifty worthies of the Church flourishing between Jerome’s time and his own. Here we end the somewhat dry enumeration of the various works of Isidore outside of his famous “twenty books of Etymologies.” This work has been aptly styled a _Konversationslexikon_, to use the excellent German word. It was named _Etymologiae_, because the author always gives the etymology of everything which he describes or defines. Indeed the tenth book contains only the etymological definitions of words alphabetically arranged. These etymologies follow the haphazard similarities of the words, and often are nonsensical. Sometimes they show a fantastic caprice indicating a mind steeped in allegorical interpretations, as, for example, when “_Amicus_ is said to be, by derivation, _animi custos_; also from _hamus_, that is, chain of love, whence we say _hami_ or hooks because they hold.”[130] This is not ignorance so much as fancy.