130 CLASSICS OF MODERN SCIENCE 

 opposed to the theory of Stahl and of many celebrated men who 

 have followed him. 



Though perhaps some of the reasons which then checked me still 

 remain today, nevertheless, the facts which have multiplied since that 

 time, and which seem to me favorable to my views, have confirmed 

 me in my opinion : though not, perhaps, any stronger, I have become 

 more confident, and I think I have sufficient proofs, or at least 

 probabilities, so that even those who may not be of my opinion can- 

 not blame me for having written. 



In general in the combustion of bodies four constant phenomena 

 are observable, which seem to be laws from which nature never de- 

 parts. Though these phenomena may be found implicitly stated in 

 other memoirs, yet I cannot dispense with recalling them here in a 

 few words. 



FIRST PHENOMENON 



All combustion sets free matter either of fire or light. 



SECOND PHENOMENON 



Bodies can burn only in a very small number of kinds of gases 

 (airs), or rather there can be combustion only in one kind of air, that 

 which Mr. Priestley has named dephlogisticated air, and which I 

 should call pure air. Not only will the bodies which we call com- 

 bustibles not burn in a vacuum or in any other kind of air, they are, 

 on the contrary, extinguished there as promptly as if they had been 

 plunged into water or any other liquid. 



THIRD PHENOMENON 



In all combustion there is destruction or decomposition of the pure 

 air in which the combustion takes place, and the body burned in- 

 creases in weight exactly in proportion to the quantity of air destroyed 

 or decomposed. 



FOURTH PHENOMENON 



In all combustion the body burned changes to an acid by the addi- 

 tion of the substance which has increased its weight: thus, for ex- 



