404 SCIENTIFIC THOUGHT. 



Prout's simple but incorrect assumption belongs to the 

 age which witnessed the decomposition of many com- 

 pounds into their two constituents by Davy's successful 

 use of the galvanic battery, at the poles of which the 

 two elements of substances made their separate appear- 

 ance. Substances which had always been considered 

 as elemental and permanent, such as many oxides and 

 earths, came to be ranged among the list of binary com- 

 pounds. This lent plausibility to the idea that even the 

 supposed elements themselves might ultimately prove to 

 be aggregates differing in number and figure of the 

 elementary particles of one and the same primary sub- 

 stance. Though with Prout's hypothesis this view has 

 been repeatedly held and refuted, another theory recom- 

 mended likewise by its simplicity had its origin in the 

 discoveries of Davy, and the further development of them 

 by Berzelius. This is the so-called electro-chemical or 

 binary theory of chemical compounds. The dual combina- 

 tion of one elementary substance with another, and again 

 of two dual compounds with each other, and so on, 

 even to the most complicated compounds, was to be the 

 simple type of chemical combination. This view, so 



atomic weight of carbon, taking called laws of phenomena. This 



oxygen as 16, was incorrect. An | consideration, so familiar to astron- 



account of the long series of deter- omers, was, I believe, quite over- 



minations of this important con- j looked in many of the best hand- 



stant will be found in the same i books during the earlier half of our 



work, p. 82, &c. I believe that in | century, and it is even yet hardly 



the first edition of this work will ' touched upon in the ordinary text- 



also be found the first consistent books. The result is an entirely 



attempt to introduce into chemical erroneous impression produced on 



data an estimate of the degree of ' the popular mind as to the degree 



accuracy or the amount of error of certainty which belongs to 



which attaches to our knowledge of scientific statements, 

 the constants of nature and the so- 



