8 ESSAYS BIOGRAPHICAL AND CHEMICAL 



script which escaped the fate of most of the Egyptian MSS. 

 of that date; for about the year 290, the Emperor 

 Diocletian commanded that all works on alchemy should 

 be burnt, * in order that the Egyptians might not become 

 rich by the art [of making gold and silver] and use their 

 wealth to revolt against the Romans.' 



But although the idea of transmutation did not arise 

 from such theoretical speculations as Aristotle's on the 

 unity of matter, and on the possibility of converting one 

 kind of matter into another by altering its properties, 

 or in the language of the time, adding or removing more 

 or less of one or other element, yet the later workers did 

 not scruple to use Aristotle's theory in order to make 

 good their case. And for many centuries indeed until 

 our own time there have always existed men who 

 devoted their lives to this object. 



There was, at the same time, a supposed mystical 

 connection, of Chaldean origin, between the metals and 

 the planets. Thus gold was the sun ; silver, the moon ; 

 copper, Venus ; tin, and afterwards mercury, was associ- 

 ated with the planet of that name ; iron, used in battle, 

 had affinity with ruddy Mars ; electron, an alloy of gold 

 and silver, and subsequently tin, was Jupiter ; and sluggish 

 and heavy lead was the slow-moving Saturn. These 

 analogies were used in casting horoscopes, or predicting 

 the future of those rich and credulous enough to consult 

 astrologers. 



At the same time as these fantastic notions were held, 

 many processes of manufacture, involving a knowledge 

 of chemical reactions, were carried on. These will be 

 alluded to later ; but it may be noted here that speculation 

 did not take the course of attempting to devise explana- 

 tions of chemical changes, but was indulged in, as 

 before remarked, with little reference to experimental 

 methods. 



