54/^B 



PREFACE. 



This is a new impression rather than a new edition of a work 

 which has been so favourably received, that the editor is 

 induced to submit it once more to the notice of the reading 

 public. The following notes on some of the tracts here 

 printed, remain nearly the same as in the other edition. 



I. Johannes de Sacro-Bosco de Arithmetica. Often occurs 

 in MSS. without his name; MSS. Harl. 3647. 3843. 4350 ; 

 Bib. Reg. 12 C. xvii ; Arund. 343. Cott. Cleop. B. vi. 

 f. 234; Publ. Cantab. Ii. I. 15. (1692). An English 

 translation — Ashm. 396. The present text is taken from 

 a manuscript formerly in the Library of the Abbate Cano- 

 nici of Venice. 



III. A Treatise on the Numeration of Algorism. — This is 

 taken from a single leaf of vellum, found loose in an old MS. 

 on astronomy, formerly in Dr. Clarke's library. 



IV. Bourne's Treatise on Optical Glasses. — The other 

 work he mentions in his dedication, as having been in- 

 scribed to Lord Burghley, is in the British Museum. — MS. 

 Sloan. 3651. 



V. Johannes Robyns de Cometis. — From a MS. in my 

 own library. Other copies, Bib. Reg. 12 B. xv. and Trin. 

 Coll. Cantab, inter MSS. Gal. O. I. 11. 



VIII. A Merchant's Account Table.— This table is ex- 

 ceedingly curious, conducted partly similar to an abacus, 

 the cyphers at the bottom being used to guide the manual 

 calculator. 



255 



