THE STORY OF NINETEENTH-CENTURY SCIENCE 



dence told for Proust and his followers, and towards the 

 close of the first decade of our century it came to be 

 generally conceded that chemical elements combine with 

 one another in fixed and definite proportions. 



More .than that. As the analysts were led to weigh 

 carefully the quantities of combining elements, it was 

 observed that the proportions are not only definite, but 

 that they bear a very curious relation to one another. 

 If element A combines with two different proportions of 

 element B to form two compounds, it appeared that the 

 weight of the larger quantity of B is an exact multiple 

 of that of the smaller quantity. This curious relation 

 was noticed by Dr. Wollaston, one of the most accurate 

 of observers, and a little later it was confirmed by Johan 

 Jakob Berzelius, the great Swedish chemist, who was to 

 be a dominating influence in the chemical world for a 

 generation to come. But this combination of elements 

 in numerical proportions was exactly what Dalton had 

 noticed as early as 1802, and what had led him directly 

 to the atomic weights. So the confirmation of this 

 essential point by chemists of such authority gave the 

 strongest confirmation to the atomic theory. 



During these same years the rising authority of the 

 French chemical world, Joseph Louis Gay-Lussac, was 

 conducting experiments with gases, which he had un- 

 dertaken at first in conjunction with Humboldt, but 

 which later on were conducted independently. In 1809, 

 the next year after the publication of the first volume 

 of Dalton's New System of Chemical Philosophy, Gay- 

 Lussac published the results of his observations, and 

 among other things brought out the remarkable fact 

 that gases, under the same conditions as to temperature 

 and pressure, combine always in definite numerical 



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