mutation, all these chapters show the stamp of solid science." Elsewhere the writer describes chemical operations, and "each description is full of special details and illustrated in the manuscript by exact figures."
Roger Bacon, too, shows us that alchemy was not intent merely upon transmutation, when he defines it as the science "concerning the generation 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 meaning 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was classed as the chief of the liberal arts; numerous treatises concerning the heavens were composed; Ptolemy's out-of-date astronomical tables were replaced by those of King Alfonso the Wise of Spain; Roger Bacon pointed out the need of reforming the calendar which Pope Gregory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
