338 POPULAR SCIENCE MONTHLY. 



nearly everywhere enriched by original observations. In his treatise De 

 Animalibus (Vol. VI. of his works) he begins by a study of the spinal 

 column, calls the sponges the lowest forms of animal life, improves 

 on the zoological classification of his forerunners, and includes good 

 descriptions of the fauna of the Arctic, and at the same time admits 

 the legendary monsters of the Bestiaires of the tenth century, the 

 barnacle-goose, anser arboreus, for example. 



His botany is said to be fuU of errors. He quotes Pliny's facts 

 relating to the fecundation of the date-palm, and correctly explains 

 them, it is believed for the first time. _ The term affinity is first used 

 in his chemical writings. There was no branch of knowledge that 

 he did not treat, from mineralogy to magnetism, and it is noteworthy 

 that he describes the magnet as in use by navigators in his time.* 



It is not necesary in this place to speak of the achievement of St. 

 Thomas Aquinas, the pupil of Albertus. His work does not lie in the 

 field of physics, but in the universe of man. His Summa treats more 

 than five hundred questions, but only one section refers to the phe- 

 nomena of the faiaterial world. One remark may be made on the 

 activity of the thirteenth century. Every one of the distinctly 

 'modern* problems was propounded in that age. Few were solved; 

 but substantially all of them were stated. When a problem is clearly 

 stated it is at least half solved. 



The most noted figure in the generation preceding Copernicus was 

 Eegiomontanus, who is always thought of in company with his col- 

 leagues Purbach and Walther. They formed part of a group of 

 German and Italian astronomers, calculators and teachers, no one of 

 whom made any signal advance, but all of whom were well instructed 

 in the fashion of the time. There are many names of men forgotten 

 to-day among this group ; but, on the other hand, the faint beginnings 

 of a critical spirit are here and there to be noted. The Almagest was 

 not always taken as infallible; observation began to be accepted as a 

 test of theory. Dominicus of Bologna, the teacher of Copernicus, is 

 a marked example of the new spirit. 



George Purbach (or Beurbach, from his native village), professor 

 of astronomy in the University of Vienna, was born in 1433 (died 

 1461), and studied at Vienna and in Italy. He was a votary of the 

 old astronomy, and his chief work, Theoncce Novce Planetarum (1460), 

 is a development of the doctrine of crystalline spheres. At the same 

 time he was an ardent student of Ptolemy. The epicycles of Ptolemy 

 were a geometrical conception; the crystalline spheres of Eudoxus and 

 Purbach a crude cosmological idea; they could not be reconciled with 

 nature. In so far Purbach was on the wrong road. He saw, how- 

 ever, the necessity for further observations of the planets and for 



* It was introduced into Europe by Flavio Gioja, according to common 

 report, about 1302. 



