376 THE CANADIAN XATURALIST. [Vol. vii. 



the heat disengaged at the moment of combinatiou. Hence that 

 conception of Lavoisier that a simple body such as oxygen is con- 

 stituted, properly speaking, by the intimate union of the ponder- 

 able matter oxygen with the imponderable fluid which constitutes 

 the principle of heat, and which he named caloric — a profound 

 conception, which modern science has adopted, giving it a differ- 

 ent form. It is, then, unjust that, in recent times, Lavoisier 

 should be accused of having misconceived what is physical in 

 the phenomenon of combustion, and that an attempt should be 

 made to rehabilitate the doctrine of Phlogiston which he had the 

 honour of overturninoj. It is true that in burnino' bodies lose 

 something: "It is the combustible principle," said the partisans 

 of Phlogiston ; "It is caloric," said Lavoisier; and he adds, an 

 essential thing, that they gain in oxygen. 



Thus Lavoisier perceived completely the phenomenon, of which 

 the great author of the phlogiston theory, G. E. Stahl, had only 

 a glimpse of the external appearances, and of which he miscon- 

 ceived the characteristic feature. Such is, gentlemen, I maintain, 

 the foundation and the origin of modern chemistry. Is that 

 to say that the monument raised upon these bases by Lavoisier 

 and his contemporaries subsists in all its parts, and that it was 

 accomplished at the end of last century ? It would not be from 

 want of materials, and even in its outlines we may notice lines 

 which have in time disappeared. It has then been added to and 

 in part transformed ; but it still rests upon the same foundations. 

 Such has been in all sciences and in all times the lot of theoretical 

 conceptions; the best of them contain obscurities and gaps which, 

 on disappearing, become the occasion of important developments 

 or of a new generalisation. 



That of Lavoisier embraced especially the bodies best known 

 in his time, i. e., the compounds of oxygen, the true nature of 

 which was discovered by him in his researches on combustion. 

 All these bodies are formed of two elements ; their constitution 

 is binary, but it is more or less complicated. Some, oxides or 

 acids, contain a simple body united to oxygen ; others, more 

 complex, are formed by the combination of acids and oxides 

 among themselves, a combination which gives rise to salts. These 

 last then are formed of two constituent parts, each of which con- 

 tains oxygen united to a simple body. Such is the formula of 

 Lavoisier on the constitution of salts ; it is in harmony with the 

 fundamental idea which he enounced on chemical combination, 



