Book digitized by Google from the library of the University of California and uploaded to the Internet Archive by user tpb. Presentation copy, signed: "the author." 1. Johannis de Sacro-Bosco Tractatus de arte numerandi.--II. A method used in England in the fifteenth century for taking the altitude of a steeple or inaccesible object.--III. A treatise on the numeration of algorism.-- IV. A treatise on the properties and qualities of glasses for optical purposes, according to the making, polishing, and grinding of them. By William Bourne.-- V. Johannis Robyns de cometis commentaria.--VI. Two tables: one shewing the time of high water at London Bridge, and the other the duration of moon-light VII. A treatise on the mensuration of heights and distances.--VIII. An account table for the use of merchants.--IX. Alexandri de Villa Dei Carmen de algorismo.--X. Prefatio Danielis de Merlai ad librum de naturis superiorum et inferiorum.--XI. Proposal for some inventions in the mechanical arts.--XII. The preface to a calendar or almanac for the year 1430.--XIII. Johannis Norfolk in artem progressionis summula.--XIV. Appendix: I. A few observations on the numerical contractions found in some manuscripts of the treatise on geometry by Boetius. II. Notes on early almanacs