284 HISTORY OF CHEMISTRY. 



not peculiarly engaged in chemical research, but who was often dis- 

 tinguished by his rapid and happy generalizations, M. Ampere. He 

 supported this analogy by many ingenious and original arguments, ir. 

 letters written to Davy, while that chemist was engaged in his re- 

 searches on fluor spar, as Davy himself declares. 2 



Still further Changes have been proposed, in that classification of 

 elementary substances to which the oxygen theory led. It has been 

 held by Berzelius and others, that other elements, as, for example, 

 sulphur, form salts with the alkaline and earthy metals, rather than 

 sulphurets. The character of these sulpho-salts, however, is still ques- 

 tioned among chemists ; and therefore it does not become us to speak 

 as if their place in history were settled. Of course, it will easily be 

 understood that, in the same manner in which the oxygen theory in- 

 troduced its own proper nomenclature, the overthrow or material trans 

 formation of the theory would require a change in the nomenclature, 

 or rather, the anomalies which tended to disturb the theory, would, as 

 they were detected, make the theoretical terms be felt as inappropriate, 

 and would suggest the necessity of a reformation in that respect. But 

 the discussion of this point belongs to a step of the science which is 

 to come before us hereafter. 



It may be observed, that in approaching the limits of this part of 

 our subject, as we are now doing, the doctrine of the combination of 

 acids and bases, of which we formerly traced the rise and progress, 

 is still assumed as a fundamental relation by which other relations are 

 tested. This remark connects the stage of chemistry now under our 

 notice with its earliest steps. But in order to point out the chemical 

 bearing of the next subjects of our narrative, we may further observe, 

 that metals, earths, salts, are spoken of as known classes of substances ; 

 and in like manner the newly-discovered elements, which form the last 

 trophies of chemistry, have been distributed into such classes accord- 

 ing to their analogies ; thus /jo/assutm, sodium, barium, have been 

 asserted to be metals ; iodine, bromine, fluorine, have been arranged 

 as analogical to chlorine. Yet there is something vague and indefinite 

 in the boundaries of such classifications and analogies and it is pre- 

 cisely where this vagueness falls, that the science is still obscure or 

 doubtful. We are led, therefore, to see the dependence of Chemistrj 

 uDon Classification ; and it is to Sciences of Classification which we 

 shall next proceed ; as soon as we have noticed the most general views 



Paris, Life of Davy, i. 870. 



