A HISTORY OF SCIENCE 



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 tem- 

 perature and pressure, combine always in definite 

 numerical proportions as to volume. Exactly two vol- 

 umes of hydrogen, for example, combine with one vol- 

 ume of oxygen to form water. Moreover, the resulting 

 compound gas always bears a simple relation to the 

 combining volumes. In the case just cited, the union of 

 two volumes of hydrogen and one of oxygen results in 

 precisely two volumes of water vapor. 



Naturally enough, the champions of the atomic theory 

 seized upon these observations of Gay-Lussac as lend- 

 ing strong support to their hypothesis all of them, 

 that is, but the curiously self-reliant and self-sufficient 

 author of the atomic theory himself, who declined to 

 accept the observations of the French chemist as valid. 

 Yet the observations of Gay-Lussac were correct, as 

 countless chemists since then have demonstrated anew, 

 and his theory of combination by volumes became one 

 of the foundation-stones of the atomic theory, despite 

 the opposition of the author of that theory. 



The true explanation of Gay-Lussac's law of com- 



42 



