5 68 THE POPULAR SCIENCE MONTHLY. 



of the basis of oxygen with caloric. It is not, then, that the one state- 

 ment, Stahlian or Lavoisierian, is false and the other true, but that 

 both of them are distorted, because incomplete. Chemists nowadays 

 are both Stahlian and Lavoisierian in their notions, or have regard 

 both to energy and matter. But Lavoisierian ideas still interfere very 

 little with our use of the Stahlian language. While we acknowledge 

 that in the act of burning the combustible and the oxygen take equal 

 part, just as in the act of falling the weight and the earth take equal 

 part, yet in our common language we alike disregard the abundant 

 atmosphere and abundant earth as being necessarily understood, and 

 speak only of the energy of the combustible and of the weight, which 

 burn and fall respectively. Whatever may be the fault of language, 

 however, chemists do not omit to superpose the Lavoisierian on the 

 Stahlian notion. They recognize fully that it is by the union of the 

 combustible with oxygen that phlogiston is dissipated in the form of 

 heat ; and, further, that phlogiston can only be restored to the burnt 

 combustible on condition of separating the combustible from the oxy- 

 gen with which it has united, just as energy of position can only be 

 restored to a fallen weight on condition of separating it to a distance 

 from the surface on which it has fallen. 



That Stahl and his followers regarded phlogiston as a material 

 substance, if they did so regard it, should interfere no more with our 

 recoo-nition of the merit due to their doctrine, than the circumstance 

 of Black and Lavoisier regarding caloric as a material substance, if 

 they- did so regard it, should interfere with our recognition of the 

 merit due to the doctrine of latent heat. But, though defining phlo- 

 giston as the principle or matter of fire, it is not at all clear that the 

 phlogistians considered this matter of fire as constituting a real body 

 or ponderable substance; but rather that they thought and spoke of it 

 as many philosophers nowadays think and speak of the electric fluid 

 and luminiferous ether. The nondescript character, properly ascriba- 

 ble to phlogiston, is indicated by the following quotation taken from 

 Macquer's "Elemens de Chymie Theorique " (1749). It must not, of 

 course, be forgotten that the popular impression as to phlogiston hav- 

 ing been conceived by its advocates as a material substance having a 

 negative weight or levity, is erroneous, and is based on an innovation 

 that was introduced during the struggling decadence of the phlogistic 

 theory, and advocated more particularly by Lavoisier's subsequent 

 colleague, Guyton de Morveau, in his " Dissertation sur le Phlogistique, 

 considere commo Corps grave, et par Rapport aux Changemens de 

 Pesanteur qu'il produit dans les Corps auxquels il est nni " (1762). 

 Macquer writes as follows : 



" ' Matter of the sun, or of light,' ' phlogiston,' ' fire,' ' sulphur-principle,' 

 ' inflammable matter ' such are the names usually employed to designate the 

 element fire. But no precise distinction appears to have been drawn between 

 fire viewed as a principle in the composition of a body, and fire when it stands 



