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 transmitted through Roman, 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 Romans 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 Roman influence did not contribute greatly to generalizing 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
