282 HISTORY OF CHEMISTRY. 



sulphurous and the sulphuric; and these acids forn, with earthy 01 

 alkaline bases, sulphites and sulphates ; while sulphur directly com- 

 bined with another element, forms a svbphuret. The term oxyd (now 

 usually written oxide) expressed a lower degree of combination with 

 oxygen than the acids. The Methods de Nomenclature Chimique was 

 published in 1787; and in 1789, Lavoisier published a treatise on 

 chemistry in order further to explain this method. In the preface to 

 this volume, he apologizes for the great amount of the changes, and 

 pleads the authority of Bergman, who had exhorted De Morveau " to 

 spare no improper names ; those who are learned will always be 

 learned, and those who are ignorant will thus learn sooner." To this 

 maxim they so far conformed, that their system offers few anomalies ; 

 and though the progress of discovery, and the consequent changes of 

 theoretical opinion, which have since gone on, appear now to require 

 a further change of nomenclature, it is no small evidence of the skill 

 with which this scheme was arranged, that for half a century it was 

 universally used, and felt to be far more useful and effective than any 

 nomenclature in any science had ever been before. 



CHAPTER VII. 

 APPLICATION AND CORRECTION OF THE OXYGEN THEORI. 



SINCE a chemical theory, as far as it is true, must enable us to 

 obtain a true view of the intimate composition of all bodies what- 

 ever, it will readily be supposed that the new chemistry led to an 

 immense number of analyses and researches of various kinds. These 

 it is not necessary to dwell upon ; nor will I even mention the names 

 of any of the intelligent and diligent men who have labored in this 

 field. Perhaps one of the most striking of such analyses was Davy's 

 decomposition of the earths and alkalies into metallic bases and oxy- 

 gen, in 1807 and 1808; thus extending still further that analogy 

 between the earths and the calces of the metals, which had had so large 

 a share in the formation of chemical theories. This discovery, how- 

 ever, both in the means by which it was made, and in the views to 

 which it led, bears upon subjects hereafter to be treated of. 



The Lavoisieriau theory also, wide as was the range of truth which 

 it embraced, required some limitation and correction. I do not now 



