By the thirteenth century, if not before, a treatise was in existence by “Hermes Mercurius Triplex” on the six principles of things[684] with a prologue concerning the three Mercuries,[685] of whom we have already heard Robert of Chester speak in his preface. Here too the first is identified with Enoch, the second with Noah, and the third is called triplex because he was at once king, philosopher, and prophet, ruling Egypt after the flood with supreme equity, renowned in both the liberal and mechanical arts, and the first to elucidate astronomy. He wrote _The Golden Bough_, _Book of Longitude and Latitude_, _Book of Election_, _Canons on the Planets_, and a treatise on the astrolabe. Among his pastimes he brought to light alchemy which the philosopher Morienus developed in his writings. _The Six Principles of Things_ is a treatise part astronomical and part astrological, considering the natures of the signs and the powers of the planets in their houses. Citations of such authors as Zahel and Dorotheus show that the work is much later than Hermes. It is followed by four other brief treatises, of which the first discusses time, the winds, pestilences, divination from thunder, and eclipses of the sun and the moon; the second and the third deal with the astrological topics, _Of the triple power of the celestial bodies_, and _Of the efficacy of medicines according to the power of the planets and the effect of the signs_. The fourth treatise tells how to use the astrolabe. [Sidenote: _Liber lune._]