Included in this work, is a general historical overview of the development of astronomical knowledge in the West from the realms of Greek scholarship in classical times through to the Renaissance and the threshold of modern physics. The subject matter of both the Irish Tract and this review extends beyond the strict confines of astronomy, encompassing the physical sciences in general. The extent of astronomical knowledge in medieval Ireland is given specific attention with a review of scholarly works in Latin since the seventh century. This includes a number of specialist studies on astronomical topics and related cosmographical fields. Also included are numerous incidental references to astronomical matters from both Irish and Latin literature during the Middle Ages. Attention is devoted to the surviving manuscript copies of the Tract and the question of its sources, origin and purpose. A possible Dominican context for the compilation and dissemination of the Tract is considered. A detailed commentary of the technical content of each chapter is presented, together with reference to contemporary developments in the West and to the occasional clues as to the institutional, geographical and chronological origins of the Tract. A study of the technical terminology used by the Irish compiler is presented in detail. Reference is made both to earlier Irish terminology where appropriate, as well as to the limitations imposed by the fact that many of the scientific concepts were yet to attain clarity that came with the advent of Newtonian physics, Copernican astronomy and post-Colombian geography. The data entries on ms Stowe B are evaluated and compared with computer generated data of astronomical movements in the 14th and 15th centuries with a view to ascertaining the time of compilation of the Tract and its working life. A A revised English translation of the Tract is included in the appendices together with Maxwell Close's unpublished commentary to relevant portions. An Irish edition, closely following the ITS edition of 1914 is also included. Corruptions to the text are footnoted together with the likely run of the original text.