562 THE POPULAR SCIENCE MONTHLY. 



The importance attached to the refutation of this theory may be 

 judged of from the circumstance that, after the early experiments of 

 Lavoisier on the composition and decomposition of water had been 

 successfully repeated by a committee of the French Academy in 1790, 

 a congratulatory meeting was held in Paris, at which Madame La- 

 voisier, attired as a priestess, burned on an altar Stahl's celebrated 

 "Fundamenta Cheruioe Dogmatics et Experimentalis," solemn music 

 playing a requiem the while. And the sort of estimation in which 

 the Stahlian doctrines have since been held by chemists is fairly illus- 

 trated by a criticism of Sir J. Herschel, who, speaking of the phlogistic 

 theory of chemistry, says that it " impeded the progress of the science, 

 as far as a science of experiment can be impeded by a false theory, 

 . . . . by involving the subject in a mist of visionary and hypotheti- 

 cal causes in place of the true acting principles." Possibly, however, 

 this much-abused theory may yet prove to contain an element of per- 

 manent vitality and truth ; anyhow the study of this earliest and most 

 enduring of chemical theories can never be wholly devoid of interest 

 to chemists. 



To appreciate the merit of the phlogistic theory it is necessary to 

 bear in mind the period of its announcement. Its originator, Beccher, 

 was born in 1625, and died a middle-aged but worn-out man in 1682, 

 a few years before the publication of the "Principia." His more for- 

 tunate disciple, Stahl, who was born in 1660, and died in 1734, in his 

 seventy-fifth year, though afforded a possibility of knowing, seems 

 equally with Beccher to have remained throughout his long career 

 indifferent to the Newtonian principle that the weight of a body is 

 proportionate to its quantity of matter that loss of weight implies of 

 necessity abstraction of matter, and increase of weight addition of 

 matter. Whether or not the founders of the phlogistic theory con- 

 ceived that change of matter in the way of kind might, equally with 

 its change in point of quantity, be associated with an alteration in 

 weight and it must not be forgotten what pains Newton thought it 

 necessary to take in order to show the contrary certain it is, they 

 attached very little importance to the changes of weight manifested 

 by bodies undergoing the metamorphosis of combustion. It might 

 be that when combustible charcoal was burned the weight of incom- 

 bustible residue was less than the original weight of charcoal it 

 might be that when combustible lead was burned the weight of in- 

 combustible residue was greater than the original weight of metal 

 this was far too trifling an unlikeness to stand in the way of the 

 paramount likeness presented by the two bodies. For the lead and 

 charcoal had the common property of manifesting the wonderful 

 energy of fire ; they could alike suffer a loss of light and heat that 

 is, of phlogiston by the deprivation of which they were alike changed 

 into greater or less weights of inert incombustible residue. 



And not only were these primitive students of the philosophy of 



