A HISTORY OF SCIENCE 



matter to a single element ; it contains, it may be, not 

 merely a germ of the science of the nineteenth-century 

 chemistry, but perhaps the germs also of the yet un- 

 developed chemistry of the twentieth century. Yet 

 we dare suggest that in their enthusiasm for the atomic 

 theory of Democritus the historians of our genera- 

 tion have done something less than justice to that 

 philosopher's precursor, Anaxagoras. And one sus- 

 pects that the mere accident of a name has been 

 instrumental in producing this result. Democritus 

 called his primordial element an atom; Anaxagoras, 

 too, conceived a primordial element, but he called it 

 merely a seed or thing ; he failed to christen it distinc- 

 tively. Modern science adopted the word atom and 

 gave it universal vogue. It owed a debt of gratitude 

 to Democritus for supplying it the word, but it some- 

 what overpaid the debt in too closely linking the new 

 meaning of the word with its old original one. For, 

 let it be clearly understood, the Daltonian atom is not 

 precisely comparable with the atom of Democritus. 

 The atom, as Democritus conceived it, was monis- 

 tic; all atoms, according to this hypothesis, are of 

 the same substance; one atom differs from another 

 merely in size and shape, but not at all in quality. 

 But the Daltonian hypothesis conceived, and nearly 

 all the experimental efforts of the nineteenth century 

 seemed to prove, that there are numerous classes of 

 atoms, each differing in its very essence from the 

 others. 



As the case stands to-day the chemist deals with 

 seventy - odd substances, which he calls elements. 

 Each one of these substances is, as he conceives it, 



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