THE EVOLUTION OF CHEMICAL TRUTH. 819 



are modified, and transformation is possible. This determinist 

 conception was afterward mingled in the minds of the alchemists 

 with Oriental mysticism; but it must be remarked that it pre- 

 sented, in the Greek philosophers Thales, Anaximenes, Heracli- 

 tus, Empedocles, Plato, and their immediate heirs, a really sci- 

 entific character. Michael Psellus was faithful to their doc- 

 trine when he wrote to the Patriarch Xiphilin, in a letter which 

 was used as the Preface to the Collection of the Greek Alchemists : 

 " The changes of nature are made naturally,, not by virtue of 

 an incantation or a miracle, or of a secret formula. There is an 

 art of transmutation. . . . You want me to teach you the art that 

 resides in fire and furnaces, and which produces the destruction 

 of substances and the transmutation of their natures. Some be- 

 lieve that this is a secret knowledge, gained by initiation, which 

 they have not tried to reduce to a rational form ; which seems to 

 me an enormous error. For myself, I try first to learn the causes, 

 and to deduce from them a rational explanation of the facts. I 

 sought it in the nature of the four elements, from which every- 

 thing comes by combination, and to which everything returns by 

 solution." 



From Greece alchemy then received, with the idea of a pri- 

 mary matter and the system of atoms, a whole contingent of 

 rationalistic notions which subsequently modified more or less 

 Christian mysticism and the traditions of the East. The effort 

 of the alchemists of the middle ages to divest the metals of their 

 individual qualities in order to reach the primitive matter, the 

 mercury of the old philosophers, was then in harmony with Pla- 

 to's metaphysics. But, in the operations they performed for that 

 end, they could only determine the indefinite transformation of 

 the elements, and they represented the mysterious process under 

 the symbolical form of a ring-serpent which has neither begin- 

 ning nor end. This hopeless picture of chemistry did not cease to 

 be true till the end of the last century. By introducing the bal- 

 ance into laboratories, Lavoisier demonstrated that the weight of 

 metals is invariable, and, in a general way, that the origin of all 

 chemical phenomena lies in the reactions of a small number of 

 undecomposable bodies, the weight and properties of which are 

 constant. 



This great discovery sapped the alchemic doctrine of the trans- 

 mutation at its very foundations. It is, however, still permissi- 

 ble to ask if the present elements, as yet undecomposed, are really 

 simple bodies. If Prout's hypothesis that they are polymers of 

 hydrogen could be demonstrated, the hope of passing from one to 

 the other would be entirely legitimate. But the recently carefully 

 made determinations of the equivalents of simple bodies by Du- 

 mas and Stas have weakened that theory. The laws of specific 



