notable works of John of Seville include the translations of a manuscript in the library of St. Marks, the Greater Introduction of Albumasar, and the engraved written work of Thebit. Another astronomical work translated by John is De compositione et utilitate astrolabii ("The composition and utility of the astrolabe") which is an instructional book explaining the construction and utilization of astrolabes. The introduction of an effective method of marking alidades, an integral component of astrolabes, was introduced through one of John's translations titled Dixit Johannes: Cum volueris facere astrolabium accipe auricalcum optimum. The work itself is originally attributed to the Arabic astronomer Mash’allah. Another significant work translated by John of Seville was Omar’s (Umar Ibn al-Farrukhân al-Tabarî) work Kitâb al-Mawâlid ("The Book of Nativities"), under the Latin title “De Nativitatibus.” Kitâb al-Mawâlid is an astrological treatise concerning “the interpretation of nativities, or birth horoscopes”. It has three separate books with quotes from other authors, including Ptolemy, Messahallah and Hermes. Another work that is attributed to John of Seville through a note in the beginning of one of the margins is from Astroligi(c)e speculationis exercitium habere volentibus, which now resides at Pommersfelden in an upper Bamberg district in Germany. Medical and Alchemy At least three of his translations, a short version of the Secretum Secretorum dedicated to a Queen Tarasia, a tract on gout offered to one of the Popes Gregory, and the original version of the 9th century Arabic philosopher Qusta ibn Luqa's De differentia spiritus et animae (The Difference Between the Spirit and the Soul), were medical translations intermixed with alchemy in the Hispano-Arabic tradition. His partial translation of the Secretum Secretorum is considered to be his earliest known work. Unlike much of his later work, this translation utilizes a first-person perspective. A lesser-known translation of his titled Speculum Elementorum, also referred to as Tractatus de perfecta et infallibili Medicina arte Akimie, was originally written by an unknown author. Another notable work translated by John of Seville from arabic is the Emerald Tablet, an alchemical work of the Hermetic tradition that is originally credited to Hermes Trismegistus himself, it was said to contain many alchemical secrets. Philosophical In his Book of Algorithms on Practical Arithmetic, John of Seville provides one of the earliest known descriptions of Indian positional notation, whose introduction to Europe is usually associated with the book Liber Abaci by Fibonacci: “A number is a collection of