•246 COSMOS. 



the Almagest. As he, hke the Arahs, always calls llippar- 

 chus Abraxis, we may conclude that he also made use of only 

 a I^atin translation from the Arabic. Next to Bacon's chem- 

 ical experiments on combustible explosive mixtures, his theo- 

 retical optical works on perspective, and the position of the 

 focus in concave mirrors, are the most important. His pro- ^ 

 found Oims Majus contains proposals and schemes of practi- 

 cable execution, but no clear traces of successful optical discov- 

 eries. Profoundness of mathematical knowledge can not be 

 ascribed to him. That which characterizes him is rather a 

 certain liveliness of fancy, which, ovv^ing to the impression ex- 

 cited by so many unexplained great natural phenomena, and 

 the long and anxious search for the solution of mysterious 

 problems, was often excited to a degree of morbid excess in 

 those monks of the Middle Ages who devoted themselves to 

 the study of natural philosophy. 



Before the invention of printing, the expense of copyists 

 rendered it difficult, in the Middle Ages, to collect any large 

 number of separate manuscripts, and thus tended to produce 

 a great predilection ibr encyclopedic works after the exten- 

 sion of ideas in the thirteenth century. These merit special 

 considoration, because they led to a generalization of ideas. 

 There appeared the twenty books Dellermn Natura of Thom- 

 as Cantipratensis, Professor at Louvain (1230) ; The Mir- 

 ror of Nature [Speculum JSaturale), written by Vincenzius of 

 Beauvais (Bellovacensis) for St. Louis and his consort Mar- 

 garet of Provence (1250) ; The Book of Nature, by Conrad 

 von Meygenberg, a priest at Pvatisbon (1349) ; and the Pic- 

 ture of the World {Imago Mu7idi) of Cardinal Petrus de AI- 

 haco, bishop of Cambray (1410), each work being in a great 

 measure based upon the preceding ones. These encyclopedic 

 compilations were the forerunners of the great work of Father 

 Pweisch, the Margarita Philosophica, the first edition of which 

 appeared in 1486, and which for half a century operated in a 

 remarkable manner on the diffusion of knowledge. I must 

 here pause for a moment to consider the " Picture of the 

 World" of Cardinal Alliacus (Pierre d'Ailly). I have else- 

 where shown that the work entitled " Imago Mundi" exer- 

 cised a greater influence on the discovery of America than 

 did the correspondence with the learned Florentine Toscanel- 

 li.* All that Columbus knew of Greek and Roman writers, 



* See my Examen Crit., t. i., p- 61, 64-70, 96-108; t. ii., p. 349 

 " There are five memoirs De Concordantia Astroiiomia cum Thealogia, 

 by Pierre cJ'Aillj vvUom Don Fernando Colon always calls Pedro de 



