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 

 oxygen as 16, was incorrect. An 

 account of the long series of deter- 

 minations of this important con- 

 stant will be found in the same 

 work, p. 82, &c. I believe that in 

 the first edition of this work will 

 also be found the first consistent 

 attempt to introduce into chemical 

 data an estimate of the degree of 

 accuracy or the amount of error 

 which attaches to our knowledge of 

 the constants of nature and the so- 



called laws of phenomena. This 

 consideration, so familiar to astrono- 

 mers, was, I believe, quite over- 

 looked in many of the best hand- 

 books during the earlier half of our 

 century, and it is even yet hardly 

 touched upon in the ordinary text- 

 books. The result is an entirely 

 erroneous impression produced on 

 the popular mind as to the degree 

 of certainty which belongs to 

 scientific statements. 



