CHAPTER IV 



ATOMS AND MOLECULES 



Perhaps no other inchoate conception had ever 

 such vitaHty as the atomic theory. Crude and 

 empiric though it were in its first beginnings, it 

 yet persisted through the centuries, waiting for 

 Dalton to complete what Democritus had begun. 



Dalton it was who, a hundred years ago, gave 

 to the atom a crown of " indivisible supremacy." 

 Dalton it was who made the atom a fact — a fact 

 to be admitted, and a fact to be used. Dalton it 

 was who brought down the atom from the clouds 

 to the laboratory and the factory. The atoms of 

 the Greeks, even the atoms of Lucretius, were 

 vague and elusive ; the atoms of Dalton were as 

 undeniable as the bricks in a wall — were indeed 

 " the foundation-stones of the universe." Higgins, 

 Richter, and one or two others hinted the atom, 

 but Dalton led it forth into the light of day ; and 

 since then " its properties and faculties, its attrac- 



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