©/ the fixed Alkalis. 1 1 1 



stinctly to show that the mature time for a complete gene- 

 ralization of chemical facts is yet far distant ; and though, 

 in the explanations of the various results of experiments that 

 have been detailed, the antiphlogistic solution of the phe- 

 nomena has been uniformly adopted, yet the motive for 

 employing it has been rather a sense of its beauty and pre- 

 cision, than a conviction of its permanency and truth. 



The discovery of the agencies of the gases destroyed the 

 hypothesis of Stahl. The knowledge of the powers and 

 effects of the ethereal substances may at a future time pos- 

 sibly act a similar part with regard to the more refined and 

 ingenious hypothesis of Lavoisier ; but in the present state 

 of our knowledge, it appears the best approximation that 

 has been made to a perfect logic of chemistry. 



Whatever future changes may take place in theory, there 

 seems however every reason to believe that the metallic bases 

 of the alkalis, and the common metals, will stand in the 

 same arrangement of substances ; and as yet we have no 

 good reasons for assuming the compound nature of this class 

 of bodies *. 



The experiments in which it is said that alkalis, metallic 

 oxides, and earths may be formed from air and water alone, 

 in processes of vegetation^ have been always made in an in- 

 conclusive manner f ; for distilled water, as I have endea- 

 voured 



* A phlogistic chemical theory might certainly be defended, on the idea, 

 that the metals are compounds of certain unknown bases with the same mat- 

 ter as that existing in hydrogen i and the metallic oxides, alkalis and acids 

 compounds of the same bases with water ; — but in this theory more unknowE 

 principles would be assumed than in the generally received theory. It w»uld 

 be less elegant and less distinct. In my first experiments on the distillation of 

 the basis of potash finding hydrogen generally produced, I was led to com- 

 pare the phlogistic hypothesis with the new facts, and I found it fully ade- 

 quate to the explanation. More delicate researches however afi er easels proved 

 that in the cases when inflammable gases appeared, water, or some body in 

 which hydrogen is admitted t& exist, was- present. 



f The explanation of Van Helmont of his fact of the production of earth 

 in the growth of the willow, was completely overturned by the researches of 

 Woodward. Phil. Trans, vol. xxi. p. 193. 



The conclusions which M. Braconnot has very lately dravrn from his m- 

 ganious experiment.*, An.-i.ale; de Chirme, Fevrier 1307, p. 1S7, are rendered of 

 iittle avail in consequence of th.e drcurastauces stated in the text. In the onlv 



case 



