W. G. STEVENSON. 93-(63) 



its tenets upon the physical, chemical and physiological 

 sciences of the age. 



Entities, of some kind, presided over the functions 

 of life and the manifestations of matter. A "vital prin- 

 ciple" ruled the organic world, and. the phenomena of 

 inorganic natnre depended upon the presence of some 

 "principle" which existed independent of the matter 

 through which it displayed itself. Material particles, 

 darting from luminous bodies into the eye, produced the 

 sensation of light. Heat and cold depended upon the 

 presence or absence of a material substance called "ca- 

 loric." Electricity was a subtile, material agent, existing 

 in a "latent" state in all substances, and manifesting 

 great power when liberated from its repose. And so 

 throughout the domain of chemical, physical and biologi- 

 cal phenomena, material entities existed and were mani- 

 fested in all forms of inorganic and organic bodies, and 

 yet were independent of them. 



This was not an age for synthetic work ; indeed, not 

 even accurate analytic work, except in simple things, 

 could be performed. These are possible only when facts 

 have been observed, and definite knowledge has been 

 acquired in special directions. 



In the sixteenth century, alchemy, having failed to 

 discover the philosopher s stone, sought to find chemical 

 remedies for diseases. Crude theories were supported 

 by a few facts wrongly interpreted. 



Early in the seventeenth century Glauber states tiiat 

 salt is the origin of all things. Boyle argues against the 

 theory that "salt, sulphur, and mercury are the princi- 

 ples of things," and makes heat a powerful factor in 

 originating new bodies. Becher thought that metals 

 consisted of earth, of which there were three kinds- 

 fusible or stony, fatty or fluid, and a ••something of 

 which they became deprived on ignition." This " some- 

 thing" Stahl named "phlogiston," which is akin to 

 "spirits" and " souls " of the alchemists. 



The phlogistic theory of Stahl was without foundation 

 in fact, and yet, based upon experimental data, it was a 

 step upward in chemical research, and held the minds 

 of all for over one hundred fifty years, including 

 such great names of the eighteenth century as Hales. 

 Black, Scheele, Priestley, Cavendish and Lavoisier. Then 



