LENGTH OF A DEGREE 7 



magistro losepio, quare sertum habeo esse castrum Mine 

 sub linea equinoxiali.® (That . . . the king of Portugal 

 sent to Guinea, in the year of our Lord 1485, Master Jo- 

 seph, his physician and astrologer, to ascertain the eleva- 

 tion of the sun in diverse places in Guinea; the said Jo- 

 seph accomplished this and reported to the said most 

 serene king, I myself being present, that among other 

 things on the nth of March he found that he was distant 

 from the equator one degree five minutes on an island 

 called "Los Ydolos," which is near Sierra Leone, and he 

 made this observation with the very greatest of care. 

 Moreover, following this, the said most serene king sent 

 to Guinea in various other places . . . and always he 

 found agreement with Master Joseph himself. This is 

 why I hold for certain that the fort of El Mina is on the 

 equator.) 



II 



Respondet quolibet gradus miliariis .56^^., idest .14. 

 leuce et .23. pasus.'^ (Each degree corresponds to 56% 

 miles, that is 14 leagues and 23 passus.) 



Ill 



Nota quod hoc anno de .88., in mense decembri, apu- 

 lit in Ulixiponam Bartholomeus Didacus, capitaneus 

 trium caravelarum, quem miserat serenissimus rex Por- 

 tugallie in Guinea ad tentandum terram; & renunciavit 

 ipso serenissimo regi prout navigaverit ultra yan naviga- 



6 Postille alia "Historia rerum ubique gestarum" di Pio II. In: Rac- 

 colta di documenti e studi pubblicati dalla R. Commissione Colombiana 

 pel Quarto Centenario dalla Scoperta dell' America, 6 parts in 14 vols.. 

 Rome, 1892-96; reference in Part I, Vol. 2, p. 369, No. 860. 



7 Postille ai trattati di P. d'Ailly: "Imago Mundi," ibid., Part I, Vol. 2, 

 p. 374, No. 4. 



