THE PATH OF EVOLUTION 



number known) as unity, all the other elements being 

 simple multiples thereof. The elements, when uniting 

 with each other and forming new compounds, did so 

 only in the ratio of these combining numbers. If a 

 greater proportion of either of the constituent elements 

 were present than formed these ratios, the excess 

 thereof remained unaffected and unchanged. The 

 number of these elements then known (1810) were 

 about forty-five, though some of them as yet existed 

 only as oxides, or otherwise in combination. This 

 theory, like most new ones, met with many opponents, 

 but he lived to see its general acceptance. Dal ton 

 never married. He said " he never had time to get 

 married." He died July 27, 1844. 



Modern Science has grouped the atoms of Dalton 

 into two classes of molecules. One formed from the 

 union of two or more atoms of the same elementary 

 nature, but constituting a body with other properties 

 than those of the single atoms such as the union of 

 three oxygen atoms to form one of. ozone ; the other 

 from the union of two or more dissimilar elementary 

 atoms into like groups. Thus the two atoms of 

 Hydrogen and one of Oxygen form one molecule of 

 water. Generally speaking, the new body thus 

 formed possesses no analogy to the properties of its 

 constituents. 



The labors of Berzelius, Gay-Lussac, Avogadro 

 172 



