CONTENTS. 



PAGE 



I. Johannis de Sacro-Bosco Tractatus de Arte Nu- 



merandi 1 



II. A method used in England in the fifteenth cen- 



tury for taking the altitude of a steeple or 

 inaccessible object 27 



III. A Treatise on the Numeration of Algorism 29 



I V. A Treatise on the properties and qualities of glasses 



for optical purposes, according to the making, 

 polishing, and grinding of them. By WILLIAM 

 BOURNE 32 



V. Johannis Robyns de Cometis Commentaria 48 



VI. Two Tables : one shewing the time of high water 



at London bridge, and the other the duration 



of moon-light. From a MS. of the 13th century. 55 



VII. A Treatise on the mensuration of heights and dis- 



tances 57 



VIII. An Account Table for the use of merchants 72 



IX. Alexandri de Villa Dei Carmen de Algorismo. ... 73 



X. Prefatio Danielis de Merlai ad librum de naturis 



superiorum et inferiorum 84 



