PREFACE. 



I HAVE thought it unnecessary to enter very fully into the 

 history of the several treatises in this volume, because it 

 will be done at large in my history of early English 

 Mathematics, now in the course of rapid preparation for the 

 press. The following notes on some of them may not prove 

 unacceptable. 



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. li. I. 15. (1692). An English 

 translation Ashm. 396. The present text is taken from 

 a MS. in my own library, purchased at the sale of the 

 Library of the Abbate Canonici 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 in my possession : from 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. 



