6 THE POPULAR SCIENCE MONTHLY 



currency system of the Empire. This work consists of recipes for the 

 testing of metals, their purification, their alloying, making of bronzes 

 and brasses, the coloring of metallic objects by superficial alloying, 

 imitations of gold, writing in gold letters, preparation of purple colors, 

 etc. Some hundred recipes in all are contained in this manuscript. It 

 is evidently based upon earlier works of similar character, and indeed 

 earlier works whose contents have been preserved to us through the 

 mediation of copies or abstracts by later writers evidence that the 

 ideas and methods were doubtless mostly centuries old when this 

 papyrus manuscript of Leyden was written. The researches of scholars, 

 notably of Berthelot, have shown how very similar, in many cases 

 identical, recipes to those of the papyrus of Leyden have been trans- 

 mitted through Eoman, Arabic and later languages in manuscript form, 

 probably uninterruptedly in Europe down to the beginning of the 

 printing of books. 



It is believed that the Greeks originally derived their knowledge of 

 the chemical arts largely from Egypt, but that the ancient Greek 

 philosophers were the first to divorce the philosophy of chemistry from 

 the religious ideas and magical notions of the Egyptian priesthood 

 which with them obscured the logical reasoning from cause to effect, 

 or from effect to cause. However that may be, the Greeks were the 

 first sources of natural philosophy for European thought. And such 

 names as Thales, Democritus, Pythagoras, Plato and Aristotle are 

 names that characterize the period of the height of clarity of Greek 

 philosophy somewhere from about 600 to 300 B.C. 



At about the time when this papyrus of Leyden was written the 

 so-called Alexandrian School of Greek philosophers was dominant. 

 This later period of Greek philosophy was marked by much brilliancy 

 and genius, but was also characterized by a distinct influence from 

 Egyptian sources of oriental mysticism and occult philosophy. 



The Eomans were the natural inheritors of Greek thought, and the 

 "Roman conquest of the civilized and much of the uncivilized world 

 again operated to spread the useful arts of chemistry as known to the 

 ancients, though Eoman influence did not contribute greatly to gen- 

 eralizing thought. 



In a.d. 489 the Alexandrian Academy was destroyed by the Emperor 

 Zeno and its Greek scholars scattered. A body of these, mainly 

 Syrians, established themselves in Persia, where they continued the 

 study and teaching of the science of the Alexandrian school. 



Barbaric invasion resulted in almost complete extinction of the 

 remains of Greek civilization in Europe. The Syrians in Persia were 

 the principal conservators of ancient science, and they continued to 

 preserve and reproduce the works of the ancient Greek writers. 



In the seventh century occurred the great Mohammedan conquest 

 of the Mediterranean countries. The conquering Moslems overran 



