284 THE POPULAR SCIENCE MONTHLY 



mutation, all these chapters show the stamp of solid science." Else- 

 where the writer describes chemical operations, and "each description 

 is full of special details and illustrated in the manuscript by exact 

 figures." 



Eoger Bacon, too, shows us that alchemy was not intent merely upon 

 transmutation, when he defines it as the science " concerning the gener- 

 ation of things from the elements, and concerning all inanimate things, 

 such as the elements and humors single and compound, ordinary stones, 

 gems, marbles, gold and other metals, sulphurs, salts, dyes and colors, 

 oils, bitumen and countless other things." The invention of gunpowder 

 has sometimes been attributed to Bacon, probably incorrectly; but he 

 mentions some explosive as already in common use in children's toy 

 caps and torpedoes. 



We have already seen that there was a good deal of scepticism about 

 the transmutation of metals in the thirteenth century. The consensus 

 of learned opinion was that most alchemists produced a mere appearance 

 of gold which would not stand severe tests. However, it was believed 

 that by reducing the metals to their constituent elements or to first 

 matter one might then combine them anew into gold. The difficulty, of 

 course, was in not realizing that the metals themselves were elements. 



Astrology was another medieval study which, like alchemy, was 

 partly scientific and partly superstitious. No clear distinction in mean- 

 ing was observed between the words astronomy and astrology. Either 

 one was used to include both knowledge of the movements of the heavenly 

 bodies and prediction of the future from them. Indeed, it was largely 

 due to this sensational and superstitious side of the subject that sober 

 astronomical observations made so much progress in both antiquity and 

 the middle ages. Astronomy in those days was the most advanced of 

 any natural science, although the Copernican theory and the telescope 

 were as yet in the future. Astronomy was classed as the chief of the 

 liberal arts ; numerous treatises concerning the heavens were composed ; 

 Ptolemy's out-of-date astronomical tables were replaced by those of King 

 Alfonso the Wise of Spain ; Eoger Bacon pointed out the need of reform- 

 ing the calendar which Pope Gregory accomplished centuries later; in 

 1344 an archbishop of Canterbury was the first to expound the correct 

 theory of polygonal stars. 



Moreover, astrology, like alchemy, became more scientific in the 

 thirteenth century than before, and it supplied what may almost be 

 called the fundamental scientific hypothesis of that period. The middle 

 ages no longer regarded the planets as gods ; and they did not so much 

 emphasize the notion that the fate of this or that man can be predicted 

 from the constellations, as they did insist that the whole world of nature 

 on our globe was controlled by the orderly, unceasing and unchanging 

 revolutions of the heavenly bodies. All generation and corruption in 



