5 66 THE POPULAR SCIENCE MONTHLY. 



vum sulphur verum arte pi-oducendi," in which he establishes what 

 may be called the permanency of chemical substance that metallic 

 lead is reproducible from the ashes of lead, sulphur verum from the 

 acid of sulphur. And, whether or not taking note of the oxidations 

 and deoxidations effected, how little differently, even at the present 

 day, would the actions referred to be described and explained ! Is it 

 not our habit to say that charcoal and sulphur and lead are bodies 

 possessing potential chemical energy that is, phlogiston ; that, in 

 the act of burning, their energy which was potential becomes kinetic 

 or dynamical, and is dissipated in the form of light and heat ; that 

 the products of their burning (including the gaseous product now 

 known to be furnished by the burning of charcoal) are substances 

 devoid of chemical energy that is, of phlogiston ; that, when the 

 acid substance furnished by burning sulphur is heated with charcoal, 

 some energy of the unburnt charcoal is transferred to the burnt sul- 

 phur, just as some energy of a raised weight may be transferred to a 

 fallen one, whereby the burnt sulphur is unburnt, provided with en- 

 ergy, and enabled to burn again, and the fallen weight is lifted up, 

 provided with energy, and enabled to fall again ; that the potential 

 chemical energy of metallic lead did not originate in the lead, but is 

 energy or phlogiston transferred thereto from the charcoal by which 

 it was smelted ; and, lastly, that the chemical energy of the charcoal 

 itself, its capability of burning, its power of doing work, in one word, 

 its phlogiston, is merely a portion of energy appropriated directly 

 from the solar rays ? 



If this be a correct interpretation of the phlogistic doctrine, it is 

 evident that the Stahlians, though ignorant of much that has since 

 become known, were nevertheless cognizant of much that became 

 afterward forgotten. For most of what has since become known 

 mankind are indebted to the surpassing genius of Lavoisier; but the 

 truth which he established, alike with that which he subverted, is now 

 recognizable as a partial truth only ; and the merit of his generaliza- 

 tion is now perceived to consist in its addition to its demerit to con- 

 sist in its supercession of the not less grand generalization estab- 

 lished by his scarcely-remembered predecessors. This being so, the 

 relationship to one another of the Stahlian and Lavoisierian theories 

 of combustion furnishes an apt illustration of the general truth set 

 forth by a great modern writer, that " in the human mind oue-sided- 

 ness has always been the rule, and many-sidedness the exception. 

 Hence, even in revolutions of opinion, one part of the truth usually 

 sets while another rises. Even progress, which ought to superadd, 

 for the most part only substitutes one partial and incomplete truth for 

 another; improvement consisting chiefly in this, that the new frag- 

 ment of truth is more wanted, more adapted to the needs of the time, 

 than that which it displaces." 



The partial truth contributed by Lavoisier was indeed more want- 



