8 1 4 THE POPULAR SCIENCE MONTHLY. 



had died from hydrophobia, and to reduce the germs through 

 numerous generations by a system of modifying treatment until 

 they have lost, in some degree, their fatal virulence, while at the 

 same fime they may have retained a protective activity within 

 the limits of safety. 



In the warfare with the pathogenic microbes the idea of em- 

 ploying certain species as our allies, and opposing them against 

 the very dangerous ones, is brilliant, and there are many facts 

 encouraging the belief that the kingdom of the microbes may 

 be further divided against itself, through the natural voracity of 

 its numerous clans. Surely any tactics and every means, agres- 

 sive and defensive, must be made available against an enemy so 

 insidious and so formidable. 



-♦♦♦- 



THE EVOLUTION OF CHEMICAL TRUTH. 



By M. LOUIS OLIVIER. 



IN" his Lectures on Chemical Philosophy, J. B. Dumas has 

 taken notice of the "singular contrast which is to be re- 

 marked among ancient peoples between the nourishing condition 

 of industrial chemistry and the entire absence of theoretical 

 chemistry." Empiricism, commanded by the necessities of ma- 

 terial life, had, in fact, to precede the disinterested speculations 

 of the reasoning powers. In this way the Phoenicians and Egyp- 

 tians made discoveries of great significance in the arts of metal- 

 lurgy, glass-working, and dyeing, without being guided by any 

 scientific light. They interpreted them in a' mystical sense, con- 

 formable to their religious conceptions of nature. Whatever we 

 may think of their theories, we can not forget the positive bases of 

 them ; for the rational science of our century has been derived 

 from their observations, winnowed by the ages. The facts have 

 resisted the assaults of time, while the magic, the theurgic doc- 

 trines, found to be sterile, have gradually disappeared to give 

 place at last to the fruitful idea of natural laws. It was a cu- 

 rious metamorphosis, in which astrology, alchemy, and the old 

 medicine predicating the virtues of stones and talismans, mark the 

 transition from the ancient to the modern mind. 



It is with great interest that we follow with M. Berthelot * the 

 evolution that has thus taken place in chemistry from the ancient 

 Orientals to the Greeks, and from them to us ; for it is associated 

 with the development of philosophical ideas, consequently with 

 the history of the human mind. From the time when alchemy 



* Les Origines de l'Alchimie (Origins of Alchemy). 



